Fujii Hiroshi

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Profile and Settings

• Name (Japanese)

  Fujii

• Name (Kana)

  Hiroshi

Degree

• Ph.D (Kyoto University), Kyoto University

Research Interests

• 電子構造
• 反応性
• 反応中間体
• タンパク質
• 酵素
• 金属イオン
• Electronic Structure
• Reactivity
• Reaction intermediate
• Protein
• Enzyme
• Metal ion

Research Areas

• Nanotechnology/Materials, Inorganic and coordination chemistry
• Life sciences, Functional biochemistry

Research Experience

• Apr. 2014, 9999, Nara Women's University, Faculty, Division of Natural Sciences, 教授
• Apr. 2014, 9999, :Professor, Graduate School of Humanities and Sciences and Department of Chemistry, Biology, and Environment Sciences, Nara Women's University
• Apr. 2007, Mar. 2014, :自然科学研究機構岡崎統合バイオサイエンスセンター 准教授
• 2007, 2014, :Associate Professor, Okazaki Institute of Integrative Bioscience, National Institutes of Natural Sciences
• Apr. 2004, Mar. 2007, :自然科学研究機構岡崎統合バイオサイエンスセンター 助教授
• 2004, 2007, :Associate Professor, Okazaki Institute of Integrative Bioscience, National Institutes of Natural Sciences
• Feb. 2001, Mar. 2004, :岡崎国立共同研究機構統合バイオサイエンスセンター 助教授
• 2001, 2004, :Associate Professor, Center for Integrative Bioscience, Okazaki National Research Institutes
• Mar. 1998, Jan. 2001, :岡崎国立共同研究機構分子科学研究所 助教授
• 1998, 2001, :Associate Professor, Institute for Molecular Science, Okazaki National Research Institutes
• Feb. 1994, Feb. 1998, :山形県テクノポリス財団生物ラジカル研究所 主任研究員
• 1994, 1998, :Chief Scientist, Yamagata Technopolis Foundation, Institute for Life Support Technology
• Nov. 1992, Jan. 1994, :ミネソタ大学化学科 博士研究員
• 1992, 1994, Post-doctoral Fellow, University of Minnesota
• Apr. 1990, Oct. 1992, :北海道大学理学部化学科 助手
• 1990, 1992, :Assistant Professor, Department of Chemistry, Faculty of Science, Hokkaido University

Education

• Apr. 1987, Mar. 1990, Kyoto University, 工学研究科, 分子工学専攻博士後期課程, Japan
• Apr. 1985, Mar. 1987, 京都大学大学院, 工学研究科, 分子工学専攻修士課程
• Apr. 1981, Mar. 1985, Kanazawa University, Faculty of Engineering, 工業化学科

Association Memberships

• 日本化学会
• アメリカ化学会
• 錯体化学会
• 日本化学会生体関連化学部会

Ⅱ．研究活動実績

Published Papers

• Refereed, in press
• Refereed, ChemBioChem., WILEY-V C H VERLAG GMBH, Photo-biohydrogen Production by Photosensitization with Biologically Precipitated Cadmium Sulfide in Hydrogen-Forming Recombinant Escherichia coli, Yuki Honda; Yuka Shinohara; Motonori Watanabe; Tatsumi Ishihara; Hiroshi Fujii, An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based onEscherichia coliwhole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinantE. colicells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. colihybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. colihybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor., Dec. 2020, 21, 23, 3389, 3397, Scientific journal, 10.1002/cbic.202000383

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• Refereed, Catalysis Science & Technology, Royal Society of Chemistry (RSC), Visible light-driven, external mediator-free H2 production by a combination of a photosensitizer and a whole-cell biocatalyst: Escherichia coli expressing [FeFe]-hydrogenase and muturase genes, Yuki Honda; Yuka Shimonhara; Hiroshi Fujii,

  A new visible light-driven, external mediator-free, and highly efficient H₂ production system is developed based on the combination of a photosensitizer and a living whole-cell biocatalyst: genetically engineered Escherichia coli.

  , Sep. 2020, 10, 17, 6006, 6012, Scientific journal, 10.1039/d0cy01099e

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• Refereed, Physical Chemistry Chemical Physics., DFT insight into axial ligand effects on electronic structure and mechanistic reactivity of oxoiron(IV) porphyrin, Zhifeng Ma; Naoki Nakatani; Hiroshi Fujii; Masahiko Hada, Jul. 2020, 22, 12173, 12179
• Refereed, J. Am. Chem. Soc., Spectroscopic Evidence for Acid-Catalyzed Disproportionation Reaction of Oxoiron(IV) Porphyrin to Oxoiron(IV) Porphyrin π-Cation Radical and Iron(III) Porphyrin, Kana Nishikawa; Yuki Honda; Hiroshi Fujii, Mar. 2020, 142, 4980, 4984
• Refereed, Bull. Chem Soc. Jpn., CHEMICAL SOC JAPAN, Effect of External Electric Fields on the Oxidation Reaction of Olefins by Fe(IV)OCl­Porphyrin Complexes, Zhifeng Ma; Naoki Nakatani; Hiroshi Fujii; Masahiko Hada, Insights of environmental perturbation (an external electric field, EEF) are complicated but important in terms of experiments. In this paper, we report theoretical results of the effect of an EEF on olefin epoxidation by an Fe(IV)OCl-porphyrin complex using density functional theory. The EEF along the electron flow greatly affects the potential energy profile, and thereby affects the reaction mechanism and stabilization of the species. The results show that a negative EEF catalyzes ethylene epoxidation, whereas a positive EEF inhibits the reaction. Moreover, an EEF can exchange the ground state with the low-lying excited states. Therefore, the potential energy profile along the epoxidation reaction is mainly modified by the electron transfer from ethylene to the Fe(IV)OCl-porphyrin complex., Feb. 2020, 93, 2, 187, 193, Scientific journal, 10.1246/bcsj.20190293

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• Refereed, Biochemistry, American Chemical Society (ACS), Unique Electronic Structures of the Highly Ruffled Hemes in Heme-Degrading Enzymes of Staphylococcus aureus, IsdG and IsdI, by Resonance Raman and Electron Paramagnetic Resonance Spectroscopies, Satoshi Takahashi; Shusuke Nambu; Toshitaka Matsui; Hiroshi Fujii; Haruto Ishikawa; Yasuhisa Mizutani; Kouhei Tsumoto; Masao Ikeda-Saito, 2020, 59, 40, 3918, 3928, Scientific journal, 10.1021/acs.biochem.0c00731

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• Refereed, Comprehesive Coordination Chemsitry III, Elsevier, Dioxygen-Binding in Metalloproteins and Corresponding Models, Shinobu Itoh; Hiroshi Fujii, 2021, 8, 200, 237, Scientific journal, 10.1016/b978-0-12-409547-2.14904-2

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• Refereed, Chemistry - A European Journal, Site-Selective Supramolecular Complexation Activates Catalytic Ethane Oxidation by a Nitrido-Bridged Iron Porphyrinoid Dimer, Nozomi Mihara; Yasuyuki Yamada; Hikaru Takaya; Yasutaka Kitagawa; Kazunobu Igawa; Katsuhiko Tomooka; Hiroshi Fujii; Kentaro Tanaka, © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 5+ , which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 5+ catalyzed ethane oxidation in the presence of H 2 O 2 at a relatively low temperature. The site-selective complexation of 3 5+ with an additional anionic porphyrin (TPPS 4− ) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 5+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS 4− to 3 5+ enhanced the catalytic activity., 01 Mar. 2019, 25, 13, 3369, 3375, Scientific journal, 10.1002/chem.201805580

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• Refereed, Inorg. Chem., Small Reorganization Energy for Ligand-Centered Electron-Transfer Reduction of Compound I to Compound II in Heme Model Study, Nami Fukui; Xiao-Xi Li; Wonwoo Nam; Shunichi Fukuzumi; Hiroshi Fujii, 2019, 58, 8263, 8266, Scientific journal
• Refereed, Angew. Chem. Int. Ed, Direct Observation of Primary C–H Bond Oxidation by An Oxido-iron(IV) Porphyrin π-Radical Cation Complex in a Fluorinated Carbon Solvent, Yuma Morimoto; Yuki; Shimaoka, Yuri; Ishimizu; Hiroshi Fujii; Shinobu Itoh, 2019, 58, 10863, 10866, Scientific journal
• Refereed, J. Biol. Inrog. Chem., Experimental and Theoretical Studies of the Porphyrin Ligand Effect on the Electronic Structure and Reactivity of Oxoiron(IV) porphyrin π-Cation Radical Complexes, Yuri Ishimizu; Zhifeng Ma; Masahiko Hada; Hiroshi Fujii, 2019, 24, 483, 494, Scientific journal
• Refereed, J. Cmput. Chem., Substitution Effects on Olefin Epoxidation Catalyzed by Oxoiron(IV) Porphyrin π-Cation Radical Complexes: A DFT Study, Zhifeng Ma; Kasumi Ukaji; Naoki Nakatani; Hiroshi Fujii; Masahiko Hada, The effects of peripheral fluorine atoms on epoxidation reactions of ethylene by oxoiron(IV) porphyrin cation radical complex in the quartet and sextet spin multiplicities are systematically investigated using the DFT method. The overall reaction routes are determined using a model system of ethylene and Fe(IV)OCl-porphyrin with substituted fluorine atoms. By obtaining the energy diagrams and electron- and spin-density difference contour maps of the transition states and intermediate compounds, we confirm that the electron-withdrawing by peripheral fluorine atoms enhances the reactivity as the number of fluorine atoms increases, as is observed experimentally. The intersystem crossing between the quartet and sextet spin multiplicities is discussed by means of the intrinsic reaction coordinate method. We conclude that the rate-determining step is located at the first transition state (TS1) for the activation of CC and FeO bonds, and the ground electronic state changes from quartet to sextet around the TS1. © 2019 Wiley Periodicals, Inc., 2019, 40, 19, 1780, 1788, Scientific journal, True, 10.1002/jcc.25831

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• Refereed, Journal of the American Chemical Society, American Chemical Society, Critical factors in determining the heterolytic versus homolytic bond cleavage of terminal oxidants by Iron(III) porphyrin complexes, Sawako Yokota; Hiroshi Fujii, Heterolytic versus homolytic cleavage of the metal-bound terminal oxidant is the key for determining the nature of reactive intermediates in metalloenzymes and metal catalyzed oxygenation reactions. Here, we study the bond cleavage process of hypochlorite by iron(III) porphyrin complexes having 4-methoxy-2,6-dimethylphenyl (1), 2,4,6-trimethylphenyl (2), 4-fluoro-2,6-dimethylphenyl (3), 2-chloro-6-methylphenyl (4), 2,6-dichlorophenyl (5), and 2,4,6-trichlorophenyl (6) groups at the meso position. Oxoiron(IV) porphyrin π-cation radical complexes (CompI) are characterized from the reactions of 1-4 with tetra-n-butylammonium hypochlorite (TBA-OCl) in dichloromethane at -80 °C, while oxoiron(IV) porphyrin complexes (CompII) are characterized for 5 and 6 under the same conditions. For all of 1-6, we find the formation of an epoxidation product in good yields from the catalytic reactions with TBA-OCl, suggesting heterolytic cleavages of the O-Cl bonds. CompI of 5 and 6 are reduced to the corresponding CompII by both chloride and hypochlorite, while CompI of 1-4 are not. The reduction reactions with hypochlorite are much faster than those with chloride. These results provide a mechanism where the O-Cl bond of the iron-bound hypochlorite is cleaved heterolytically to form CompI for all of 1-6, but the subsequent reduction reaction with remaining hypochlorite affords CompII for 5 and 6. The E(OCl•/OCl-) value is the boundary to discriminate the identity of the final product: CompI or CompII. Thermodynamic analysis based on the redox potential is successfully applied for explaining the bond cleavage processes of the hypochlorite, hydroperoxide, and tert-butyl peroxide complexes., 18 Apr. 2018, 140, 15, 5127, 5137, Scientific journal, 10.1021/jacs.7b13037

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• Not Refereed, Inorganic Chemistry, American Chemical Society, Preparation, Characterization and Reactivity of a Bis-hypochlorite Adduct of a Chiral Manganese(IV) Salen Complex, Ikuko Araki; Kaoru Fukui; Hiroshi Fujii, A bis-hypochlorite adduct of a manganese(IV) salen complex having a chiral (R,R)-cyclohexane-1,2-diamine linkage (2-tBu) is successfully prepared and characterized by various spectroscopic methods. The reactions of 2-tBu with various organic substrates show that 2-tBu is capable of sulfoxidation, epoxidation, chlorination, and hydrogen abstraction reactions. However, the enantioselectivity of the epoxidation reactions by 2-tBu is much lower than that reported for the catalytic reactions by Jacobsen's catalyst. The low enantioselectivity is consistent with a planar conformation of the salen ligand, which is suggested by circular dichroism spectroscopy. This study suggests that 2-tBu is not a reactive intermediate of Jacobsen's enantioselective epoxidation catalysis., 19 Feb. 2018, 57, 4, 1685, 1688, Scientific journal, 10.1021/acs.inorgchem.7b02661

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• Refereed, ChemBioChem, Coexpression of 5-aminolevulinic Acid Synthase Gene Facilitates Heterologous Production of Thermostable Cytochrome P450, CYP119, in Holo Form in Escherichia coli, Yuki Honda; Ki Nanasawa; Hiroshi Fujii, 2018, 19, 2156, 2159, Scientific journal
• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Participation of Electron Transfer Process in Rate-Limiting Step of Aromatic Hydroxylation Reactions by Compound I Models of Heme Enzymes, Maaya Asaka; Hiroshi Fujii, Hydroxylation reactions of aromatic rings are key reactions in various biological and chemical processes. In spite of their significance, no consensus mechanism has been established. Here we performed Marcus plot analysis for aromatic hydroxylation reactions with oxoiron(IV) porphyrin pi-cation radical complexes (compound I). Although many recent studies support the mechanism involving direct electrophilic attack of compound I, the slopes of the Marcus plots indicate a significant contribution of an electron transfer process in the rate-limiting step, leading us to propose a new reaction mechanism in which the electron transfer process between an aromatic compound and compound I is in equilibrium in a solvent cage and coupled with the subsequent bond formation process., Jul. 2016, 138, 26, 8048, 8051, Scientific journal, 10.1021/jacs.6b03223

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• Not Refereed, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, The Origin of Relative Stability of Di-mu-oxo M-M Chiral Salen Complexes [M-M = Ti(TV)-Ti(IV), V(IV)-V(IV), Cr(IV)-Cr(IV), and Mn(IV) Mn(IV)]: A Quantum-Chemical Analysis, Radhika Narayanan; Archana Velloth; Takuya Kurahashi; Hiroshi Fujii; Masahiko Hada, Di-mu-oxo dimetal cores can form Binuclear complexes with definite stereochemistries. Recent studies describing the synthesis and evaluation of titanium(IV) and manganese(IV) di-mu-oxo dimetal chiral salen complexes prompted us to explore the corresponding vanadium(IV) and chromium(IV) complexes. We therefore modeled a series of di-mu-oxo dimetal complexes of titanium(IV), vanadium(IV), chromium(IV), and manganese(IV) with tetradentate salen ligands bearing different degrees of steric bulk. Quantum mechanical calculations were conducted to compare the stabilities and molecular structures of these complexes. The results of natural population analysis gave an insight into the charge distribution characteristics of the di-mu-oxo dimetal cores of these complexes. Our calculations showed that the di-mu-oxo dimetal complexes bearing the least sterically encumbered model ligand 1 preferred the M-helical form over the P-helical one. In the titanium(IV) and chromium(IV) complexes containing a practical chiral salen ligand 2, the P-helical form was found to be more stable than the corresponding M-form. In contrast, the corresponding vanadium(IV) and manganese(IV) complexes preferred to exist in the M-helical form. The degree of distortion of the di-mu-oxo dimetal core and the inter ligand interactions were key factors for determining the stability of these complexes., Apr. 2016, 89, 4, 447, 454, Scientific journal, 10.1246/bcsj.20150393

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• Not Refereed, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, NATL ACAD SCIENCES, Unique coupling of mono- and dioxygenase chemistries in a single active site promotes heme degradation, Toshitaka Matsui; Shusuke Nambu; Celia W. Goulding; Satoshi Takahashi; Hiroshi Fujii; Masao Ikeda-Saito, Bacterial pathogens must acquire host iron for survival and colonization. Because free iron is restricted in the host, numerous pathogens have evolved to overcome this limitation by using a family of monooxygenases that mediate the oxidative cleavage of heme into biliverdin, carbon monoxide, and iron. However, the etiological agent of tuberculosis, Mycobacterium tuberculosis, accomplishes this task without generating carbon monoxide, which potentially induces its latent state. Here we show that this unusual heme degradation reaction proceeds through sequential mono- and dioxygenation events within the single active center of MhuD, a mechanism unparalleled in enzyme catalysis. A key intermediate of the MhuD reaction is found to be meso-hydroxyheme, which reacts with O-2 at an unusual position to completely suppress its monooxygenation but to allow ring cleavage through dioxygenation. This mechanistic change, possibly due to heavy steric deformation of hydroxyheme, rationally explains the unique heme catabolites of MhuD. Coexistence of mechanistically distinct functions is a previously unidentified strategy to expand the physiological outcome of enzymes, and may be applied to engineer unique biocatalysts., Apr. 2016, 113, 14, 3779, 3784, Scientific journal, 10.1073/pnas.1523333113

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• Not Refereed, CHEMICAL SCIENCE, ROYAL SOC CHEMISTRY, The functional role of the structure of the dioxo-isobacteriochlorin in the catalytic site of cytochrome cd(1) for the reduction of nitrite, Hiroshi Fujii; Daisuke Yamaki; Takashi Ogura; Masahiko Hada, Cytochrome cd(1) is a key enzyme in bacterial denitrification and catalyzes one-electron reduction of nitrite (NO2-) to nitric oxide (NO) at the heme d(1) center under anaerobic conditions. The heme d(1) has a unique dioxo-isobacteriochlorin structure and is present only in cytochrome cd(1). To reveal the functional role of the unique heme d1 in the catalytic nitrite reduction, we studied effect of the porphyrin macrocycle on each reaction step of the catalytic cycle of cytochrome cd(1) using synthetic model complexes. The complexes investigated are iron complexes of dioxo-octaethylisobacteriochlorin (1), mono-oxooctaethylchlorin (2) and octaethylporphyrin (3). We show here that the reduction potential for the transition from the ferric state to the ferrous state and the binding constant for binding of NO2- to the ferrous complex increases with a trend of 3 < 2 < 1. However, the reactivity of the ferrous nitrite complex with protons increases in the reversed order, 1 < 2 < 3. We also show that the iron bound NO of the ferric NO complex is readily replaced by addition of 1 equiv. of p-nitrophenolate. These results indicate that the dioxo-isobacteriochlorin structure is superior to porphyrin and mono-oxo-chlorin structures in the first iron reduction step, the second nitrite binding step, and the NO dissociation step, but inferior in the third nitrite reduction step. These results suggest that the heme d(1) has evolved as the catalytic site of cytochrome cd(1) to catalyze the nitrite reduction at the highest possible redox potential while maintaining its catalytic activity., 2016, 7, 4, 2896, 2906, Scientific journal, 10.1039/c5sc04825g

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Factors Affecting Hydrogen-Tunneling Contribution in Hydroxylation Reactions Promoted by Oxoiron(IV) Porphyrin pi-Cation Radical Complexes, Zhiqi Cong; Haruki Kinemuchi; Takuya Kurahashi; Hiroshi Fujii, Hydrogen atom transfer with a tunneling effect (H-tunneling) has been proposed to be involved in aliphatic hydroxylation reactions catalyzed by cytochrome P450 and synthetic heme complexes as a result of the observation of large hydrogen/deuterium kinetic isotope effects (KIEs). In the present work, we investigate the factors controlling the H-tunneling contribution to the H-transfer process in hydroxylation reaction by examining the kinetics of hydroxylation reactions at the benzylic positions of xanthene and 1,2,3,4-tetrahydronaphthalene by oxoiron(IV) 5,10,15,20-tetramesitylporphyrin pi-cation radical complexes ((TMP+center dot)(FeO)-O-IV(L)) under single-turnover conditions. The Arrhenius plots for these hydroxylation reactions of H-isotopomers have upwardly concave profiles. The Arrhenius plots of D-isotopomers, clear isosbestic points, and product analysis rule out the participation of thermally dependent other reaction processes in the concave profiles. These results provide evidence for the involvement of H-tunneling in the rate-limiting H-transfer process. These profiles are simulated using an equation derived from Bell's tunneling model. The temperature dependence of the KIE values (k(H)/k(D))) determined for these reactions indicates that the KIE value increases as the reaction temperature becomes lower, the bond dissociation energy (BDE) of the C-H bond of a substrate becomes higher, and the reactivity of (TMP+center dot)(FeO)-O-IV(L) decreases. In addition, we found correlation of the slope of the 1n(k(H)/k(D)) - 1/T plot and the bond strengths of the Fe=O bond of (TMP+center dot)(FeO)-O-IV(L) estimated from resonance Raman spectroscopy. These observations indicate that these factors modulate the extent of the H-tunneling contribution by modulating the ratio of the height and thickness of the reaction barrier., Oct. 2014, 53, 19, 10632, 10641, Scientific journal, 10.1021/ic501737j

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• Not Refereed, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, AMER CHEMICAL SOC, Theoretical Study of One-Electron Oxidized Mn(III)- and Ni(II)-Salen Complexes: Localized vs Delocalized Ground and Excited States in Solution, Shinji Aono; Masayuki Nakagaki; Takuya Kurahashi; Hiroshi Fujii; Shigeyoshi Sakaki, One-electron oxidized Mn(III)- and Ni(II)-salen complexes exhibit unique mixed-valence electronic structures and charge transfer (CT) absorption spectra. We theoretically investigated them to elucidate the reason why the Mn(III)-salen complex takes a localized electronic structure (class II mixed valence compound by Robin Day classification) and the Ni(II)-analogue has a delocalized one (class III) in solution, where solvation effect was taken into consideration either by the three-dimensional reference interaction site model self-consistent field (3D-RISM-SCF) method or by the mean-field (MF) QM/MM-MD simulation. The geometries of these complexes were optimized by the 3D-RISM-SCF-U-DFT/M06. The vertical excitation energy and the oscillator strength of the first excited state were evaluated by the general multiconfiguration reference quasi-degenerate perturbation theory (GMC-QDPT), including the solvation effect based on either 3D-RISM-SCF- or MF-QM/MM-MD-optimized solvent distribution. The computational results well agree with the experimentally observed absorption spectra and the experimentally proposed electronic structures. The one-electron oxidized Mn(III) salen complex with a symmetrical salen ligand belongs to the class II, as experimentally reported, in which the excitation from the phenolate anion to the phenoxyl radical moiety occurs. In contrast, the one-electron oxidized Ni(II)-salen complex belongs to the class III, in which the excitation occurs from the doubly occupied delocalized pi(1) orbital of the salen radical to the singly occupied delocalized pi(2) orbital; the pi(1) is a bonding combination of the HOMOs of two phenolate moieties and the pi(2) is an antibonding combination. Solvation effect is indispensable for correctly describing the mixed-valence character, the geometrical distortion, and the intervalence CT absorption spectra of these complexes. The number of d electrons and the d orbital energy level play crucial roles to provide the localization/delocalization character of these complexes., Mar. 2014, 10, 3, 1062, 1073, Scientific journal, 10.1021/ct401014p

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• Not Refereed, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, SPRINGER, Synthesis, Characterization, and Reactivity of Hypochlorito-Iron(III) Porphyrin Complexes, H. Fujii; Z. Cong; T. Kurahashi; S. Yanagisawa; T. Ogura, Mar. 2014, 19, S159, S159
• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Di-mu-oxo Dimetal Core of Mn-IV and Ti-IV as a Linker Between Two Chiral Salen Complexes Leading to the Stereoselective Formation of Different M- and P-Helical Structures, Takuya Kurahashi; Masahiko Hada; Hiroshi Fujii, Because of restricted rotational freedom along the metal-metal axis, a di-mu-oxo dimetal core could be an excellent building block to create dinuclear compounds with well-defined stereochemistry, but their stereoselective synthesis remains a challenge. We herein report the formation of di-mu-oxo dimanganese(IV) complexes with tetradentate salen ligands bearing different degrees of steric bulk, in order to study stereochemical aspects of the dimerization reaction that potentially generates multiple stereoisomers. Xray crystallography shows that the di-mu-oxo dimanganese(IV) complex with salen, where salen is (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine, adopts a unique structure in which two salen complexes are arranged in an M-helical fashion. According to the solution study using H-1, H-2 NMR, and circular dichroism spectroscopies, the dimerization reaction is highly diastereoselective in the presence of the tert-butyl group at the 3/3' position as a determinant steric factor. In contrast, the di-mu-oxo dititanium(IV) complex with the same salen ligand was previously reported to afford an opposite P-helical dimer. The present DFT study clarifies that a less-covalent Ti-O bonding causes a distortion of the di-mu-oxo dititanium(IV) core structure, generating a completely different framework for interligand interaction. The present study provides a solid basis to understand the stereochemistry for the formation of the di-mu-oxo dimetal core., Jan. 2014, 53, 2, 1070, 1079, Scientific journal, 10.1021/ic402572h

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Oxygen-Atom Transfer from Iodosylarene Adducts of a Manganese(IV) Salen Complex: Effect of Arenes and Anions on I(III) of the Coordinated Iodosylarene, Chunlan Wang; Takuya Kurahashi; Kensuke Inomata; Masahiko Hada; Hiroshi Fujii, This paper reports preparation, characterization, and reactivity of iodosylarene adducts of a manganese(IV) salen complex. In order to systematically investigate steric and electronic factors that control reactivity and selectivity, we prepared iodosylarene adducts from iodosylbenzene, iodosylmesitylene, 2,4,6-triethyliodosylbenzene, and pentafluoroiodosylbenzene. We also investigated the effect of anions on I(III) by using chloride, benzoate, and p-toluenesulfonate. Spectroscopic studies using H-1 NMR, electron paramagnetic resonance, infrared spectroscopy, and electrospray ionization mass spectrometry show that these iodosylarene adducts are manganese(IV) complexes bearing two iodosylarenes as external axial ligands. Reactions with thioanisole under the pseudo-first-order conditions show that the electron-withdrawing pentafluorophenyl group and the p-toluenesulfonate anion on I(III) significantly accelerate the oxygen-atom transfer. The high reactivity is correlated with a weakened I-OMn bond, as indicated by IR spectroscopy and mass spectrometry. Stoichiometric reactions with styrenes show that both enantioselectivity and diastereoselectivity are dependent on the arenes and anions on I(III) of the coordinate iodosylarenes. Notably, the pentafluorophenyl group and the p-toluenesulfonate anion suppress the cis-to-trans isomerization in the epoxidation of cis-beta-methylstyrene. The present results show that iodosylarene adducts of manganese(IV) salen complexes are indeed active oxygen-atom-transfer reagents and that their reactivity and selectivity are regulated by steric and electronic properties of the arenes and anions on I(III) of the coordinated iodosylarenes., Aug. 2013, 52, 16, 9557, 9566, Scientific journal, 10.1021/ic401270j

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Unique Ligand-Radical Character of an Activated Cobalt Salen Catalyst That Is Generated by Aerobic Oxidation of a Cobalt(II) Salen Complex, Takuya Kurahashi; Hiroshi Fujii, The Co(salen)(X) complex, where salen is chiral N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine and X is an external axial ligand, has been widely utilized as a versatile catalyst. The Co(salen)(X) complex is a stable solid that has been conventionally described as a Co-III(salen)(X) complex. Recent theoretical calculations raised a new proposal that the Co(salen)(H2O)(SbF6) complex contains appreciable contribution from a Co-II(salen(circle+)) electronic structure (Kochem, A.; Kanso, H.; Baptiste, B.; Arora, H.; Philouze, C.; Jarjayes, O.; Vezin, H.; Luneau, D.; Orb, M.; Thomas, F. Inorg. Chem. 2012, 51, 10557-10571), while other theoretical calculations for Co(salen)(Cl) indicated a triplet Co-III(salen) electronic structure (Kemper, S.; Hrobarik, P.; Kaupp, M.; Schlorer, N. E. J. Am. Chem. Soc. 2009, 131, 4172-4173). However, there have been no experimental data to evaluate these theoretical proposals. We herein report key experimental data on the electronic structure of the Co(salen)(X) complex (X = CF3SO3-, SbF6-, and p-MeC6H4SO3-). The X-ray crystallography shows that Co(salen)(OTf) has a square-planar N2O2 equatorial coordination sphere with OTf as an elongated external axial ligand. Magnetic susceptibility data indicate that Co(salen)(OTf) complexes belong to the S = 1 spin system. H-1 NMR measurements provide convincing evidence for the Co-II(salen(circle+))(X) character, which is estimated to be about 40% in addition to 60% Co-III(salen)(X) character. The CH2Cl2 solution of Co(salen)(X) shows an intense near-IR absorption, which is assigned as overlapped transitions from a ligand-to-metal charge transfer in Co-III(salen)(X) and a ligand-to-ligand charge transfer in Co-II(salen(circle+))(X). The present experimental study establishes that the electronic structure of Co(salen)(X) contains both Co-II(salen(circle+))(X) and Co-III(salen)(X) character., Apr. 2013, 52, 7, 3908, 3919, Scientific journal, 10.1021/ic302677f

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• Not Refereed, 錯体化学会誌, 酸化反応に関わる金属酵素からみた生物無機化学の展望, 藤井 浩, 2013, 62
• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Synthesis, Characterization, and Reactivity of Hypochloritoiron(III) Porphyrin Complexes, Zhiqi Cong; Sachiko Yanagisawa; Takuya Kurahashi; Takashi Ogura; Satoru Nakashima; Hiroshi Fujii, A hypochloritoiron(III) porphyrin species has been proposed as a key intermediate in an antimicrobial defense system in neutrophils and in hemecatalyzed chlorination reactions. We report herein the preparation, spectroscopic characterization, and reactivity of the bis(hypochlorito)iron(III) porphyrin complex [(TPFP)Fe-III(OC1)(2)](-) (1) and the imidazole-hypochloritoiron complexes (TPFP)Fe-III(OC1)(1-R-Im) [R = CH3 (2), H (3), CH2CO2H (4)], in which TPFP is 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinate. The structures of 1-4 were confirmed by absorption, H-2 and F-19 NMR, EPR, and resonance Raman spectroscopy and electrospray ionization mass spectrometry at low temperature. The reactions of 1 and 2 with various organic substrates show that 1 and 2 are capable of chlorination, sulfoxidation, and epoxidation reactions and that 1 is much more reactive with these substrates than 2., Dec. 2012, 134, 51, 20617, 20620, Scientific journal, 10.1021/ja3108774

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• Not Refereed, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, Comparative Spectroscopic Studies of Iron(III) and Manganese(III) Salen Complexes Having a Weakly Coordinating Triflate Axial Ligand, Takuya Kurahashi; Hiroshi Fujii, We thoroughly compared spectroscopic and magnetic properties of mononuclear iron(III) and manganese(III) complexes with symmetric and nonsymmetrical salen ligands, in order to investigate the relation between spectroscopic properties and electronic structures. Magnetic susceptibility and dual-mode electron paramagnetic resonance data show the assignment of [Fe-III(salen)(OTf)] and [Mn-III(salen)(OTf)] as high-spin S = 5/2 and S = 2 electronic configurations, respectively, irrespective of the electron-donating properties and symmetry of the salen ligand. Further insights into electronic structures of central metal are obtained from H-2 NMR spectra of selectively deuterated complexes, in which [Fe-III(salen)(OTf)] and [Mn-III(salen)(OTf] exhibit well-resolved paramagnetic NMR signals of quite different shift patterns, due to the presence or absence of the unpaired electron in the d(x2-y2) orbital expected for S = 5/2 iron(III) or S = 2 manganese(III) centers., Sep. 2012, 85, 9, 940, 947, Scientific journal, 10.1246/bcsj.20120146

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Effect of the Axial Ligand on the Reactivity of the Oxoiron(IV) Porphyrin pi-Cation Radical Complex: Higher Stabilization of the Product State Relative to the Reactant State, Akihiro Takahashi; Daisuke Yamaki; Kenichiro Ikemura; Takuya Kurahashi; Takashi Ogura; Masahiko Hada; Hiroshi Fujii, The proximal heme axial ligand plays an important role in tuning the reactivity of oxoiron(IV) porphyrin pi-cation radical species (compound I) in enzymatic and catalytic oxygenation reactions. To reveal the essence of the axial ligand effect on the-reactivity, we investigated it from a thermodynamic viewpoint. Compound I model complexes, (TMP+center dot)(FeO)-O-IV(L) (where TMP is 5,10,15,20-tetrarnesitylporphyrin and TMP+center dot is its pi-cation radical), can be provided with altered reactivity by changing the identity of the axial ligand, but the reactivity is not correlated with spectroscopic data (nu(Fe=O), redox potential, and so on) of (TMP+center dot)(FeO)-O-IV(L). Surprisingly, a clear correlation was found between the reactivity of (TMP+center dot)(FeO)-O-IV(L) and the Fe-II/Fe-III redox potential of (TMP)(FeL)-L-III, the final reaction product. This suggests that the thermodynamic stability of (TMP)(FeL)-L-III is involved in the mechanism of the axial ligand effect. Axial ligand-exchange experiments and theoretical calculations demonstrate a linear free-energy relationship, in which the axial ligand modulates the reaction free energy by changing the thermodynamic stability of (TMP)Fe-III(L) to a greater extent than (TMP+center dot)(FeO)-O-IV(L). The linear free energy relationship could be found for a wide range of anionic axial ligands and for various types of reactions, such as epoxidation, demethylation, and hydrogen abstraction reactions. The essence of the axial ligand effect is neither the electron donor ability of the axial ligand nor the electron affinity of compound I, but the binding ability of the axial ligand (the stabilization by the axial ligand). An axial ligand that binds more strongly makes (TMP)Fe-III(L) more stable and (TMP+center dot)(FeO)-O-IV(L) more reactive. All results indicate that the axial ligand controls the reactivity of compound I (the stability of the transition state) by the stability of the ground state of the final reaction product and not by compound I itself., Jul. 2012, 51, 13, 7296, 7305, Scientific journal, 10.1021/ic3006597

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• Not Refereed, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, Coordination and Electronic Structure of Ruthenium(II)-tris-2,2 '-bipyridine in the Triplet Metal-to-Ligand Charge-Transfer Excited State Observed by Picosecond Time-Resolved Ru K-Edge XAFS, Tokushi Sato; Shunsuke Nozawa; Ayana Tomita; Manabu Hoshino; Shin-ya Koshihara; Hiroshi Fujii; Shin-ichi Adachi, Time-resolved X-ray absorption spectra of photoexcited nithenium(H)-tris-2,2'-bipyridine ([Ru-II(bpy)(3)](2+) in the triplet metal-to-ligand charge transfer ((MLCT)-M-3) state are measured and analyzed to investigate transient structural changes directly related to the photophysical properties of the complex. The results from visible (400 rim) and UV (267 nm) excitation indicate that electrostatic interaction between the oxidized Ru atom and the reduced bipyridine ligand is the dominant factor affecting the Ru-N bond contraction. This thus leads to two groups of Ru ligand distances, one exhibiting the ground-state Ru-N distance and another yielding a slightly decreased Ru-N distance due to the localized MLCT excited state. The EXAFS analysis of the photoexcited complex was analyzed toward one single Ru-N distance., yielding a contraction of 0.04 (0.01) angstrom with an increased DW factor (corresponding to a 0.05 angstrom mean increase)., Jul. 2012, 116, 27, 14232, 14236, Scientific journal, 10.1021/jp3038285

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Formation of Iron(III) meso-Chloro-isoporphyrin as a Reactive Chlorinating Agent from Oxoiron(IV) Porphyrin pi-Cation Radical, Zhiqi Cong; Takuya Kurahashi; Hiroshi Fujii, Iron(III) isoporphyrin, a tautomer of porphyrin with a saturated meso carbon, is one of the isoelectronic forms of oxoiron(IV) porphyrin pi-cation radical, which is known as an important reactive intermediate of various heme enzymes. The isoporphyrin has been believed to be incapable of catalyzing oxygenation and oxidation reactions. Here, we report that an oxoiron(IV) porphyrin pi-cation radical can be converted to iron(III) meso-chloro-isoporphyrin in the presence of trifluoroacetic acid and chloride ion. More importantly, this study shows the first evidence that iron(III) meso-chloro-isoporphyrin is an excellent reactive agent for chlorinating aromatic compounds and olefins. The results of this study suggest that the mechanism involves electrophilic chlorination of substrate with iron(III) meso-chloro-isoporphyrin., Mar. 2012, 134, 10, 4469, 4472, Scientific journal, 10.1021/ja209985v

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, Structure and Reactivity of an Iodosylarene Adduct of a Manganese(IV)-Salen Complex, Chunlan Wang; Takuya Kurahashi; Hiroshi Fujii, 2012, 51, 31, 7809, 7811, Scientific journal, 10.1002/anie.201202835

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• Not Refereed, CHEMICAL SCIENCE, ROYAL SOC CHEMISTRY, Solid-state O-17 NMR and computational studies of terminal transition metal oxo compounds, Jianfeng Zhu; Takuya Kurahashi; Hiroshi Fujii; Gang Wu, We report solid-state NMR characterization of the O-17 (I = 5/2) chemical shift and quadrupole coupling tensors in two terminal oxo compounds, O-17 Ti(IV)(TMP) and O-17 Cr(IV)(TMP), in which TMP is 5,10,15,20-tetramesitylporphyrin and the oxo ligand is enriched by O-17 (ca. 40%). This is the first time that O-17 NMR tensors are determined for this important class of compounds. The O-17 nuclei in the O Ti and O Cr triple bonds are found to exhibit very large chemical shift anisotropies but rather small O-17 quadrupole coupling constants. Terminal oxo compounds represent one of the rare cases where the atomic nucleus under study simultaneously experiences a highly anisotropic magnetic shielding environment, but a highly symmetrical electric field distribution. The solid-state O-17 NMR data are consistent with solid-state C-13, N-15 and P-31 NMR results on carbido, nitrido and phosphido compounds. The density functional theory (DFT) computations using the zeroth-order regular approximation (ZORA) to account for spin-orbital relativistic effects reproduce the experimental O-17 NMR results reasonably well. DFT computations also reveal the origins at the molecular orbital level of the observed O-17 NMR properties for terminal oxo compounds., 2012, 3, 2, 391, 397, Scientific journal, 10.1039/c1sc00725d

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Redox Potentials of Oxoiron(IV) Porphyrin pi-Cation Radical Complexes: Participation of Electron Transfer Process in Oxygenation Reactions, Akihiro Takahashi; Takuya Kurahashi; Hiroshi Fujii, The oxoiron(IV) porphyrin pi-cation radical complex (compound I) has been identified as the key reactive intermediate of several heme enzymes and synthetic heme complexes. The redox properties of this reactive species are not yet well understood. Here, we report the results of a systematic study of the electrochemistry of oxoiron(IV) porphyrin pi-cation radical complexes with various porphyrin structures and axial ligands in organic solvents at low temperatures. The cyclic voltammogram of (TMP)Fe(IV)O, (TMP = 5,10,15,20-tetramesitylporphyrinate), exhibits two quasi-reversible redox waves at E(1/2) = 0.88 and 1.18 V vs SCE in dichloromethane at similar to 60 degrees C. Absorption spectral measurements for electrochemical oxidation at controlled potential clearly indicated that the first redox wave results from the (TMP)Fe(IV)O/[TMP(+circle))Fe(IV)O](+) couple. The redox potential for the (TMP)Fe(IV)O/[(TMP(+circle))Fe(IV)O](+) couple undergoes a positive shift upon coordination of an anionic axial ligand but a negative shift upon coordination of a neutral axial ligand (imidazole). The negative shifts of the redox potential for the imidazole complexes are contrary to their high oxygenation activity. On the other hand, the electron-withdrawing effect of the meso-substituent shifts the redox potential in a positive direction. Comparison of the, measured redox potentials and reaction rate constants for epoxidation of cyclooctene and demethylation of N,N-dimethylanilines enable us to discuss the details of the electron transfer process from substrates to the oxoiron(IV) porphyrin pi-cation radical complex in the oxygenation mechanisms., Aug. 2011, 50, 15, 6922, 6928, Scientific journal, 10.1021/ic102564e

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, One-Electron Oxidation of Electronically Diverse Manganese(III) and Nickel(II) Salen Complexes: Transition from Localized to Delocalized Mixed-Valence Ligand Radicals, Takuya Kurahashi; Hiroshi Fujii, Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to a remote phenolate via a neighboring redox-active metal ion, providing an opportunity to study electron transfer from a phenolate to a phenoxyl radical mediated by a redox-active metal ion as a bridge. We herein synthesize one-electron-oxidized products from electronically diverse manganese(III) salen complexes in which the locus of oxidation is shown to be ligand-centered, not metal-centered, affording manganese(III) phenoxyl radical species. The key point in the present study is an unambiguous assignment of intervalence charge transfer bands by using nonsymmetrical salen complexes, which enables us to obtain otherwise inaccessible insight into the mixed-valence property. A d(4) high-spin manganese (III) ion forms a Robin Day class II mixed-valence system, in which electron transfer is occurring between the localized phenoxyl radical and the phenolate. This is in clear contrast to a d(8) low-spin nickel(II) ion with the same salen ligand, which induces a delocalized radical (Robin Day class III) over the two phenolate rings, as previously reported by others. The present findings point to a fascinating possibility that electron transfer could be drastically modulated by exchanging the metal ion that bridges the two redox centers., Jun. 2011, 133, 21, 8307, 8316, Scientific journal, 10.1021/ja2016813

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-BLACKWELL, Oxidation of Chloride and Subsequent Chlorination of Organic Compounds by Oxoiron(IV) Porphyrin pi-Cation Radicals, Zhiqi Cong; Takuya Kurahashi; Hiroshi Fujii, 2011, 50, 42, 9935, 9939, Scientific journal, 10.1002/anie.201104461

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• Not Refereed, Bull. Jpn. Soc. Coord. Chem., Japan Society of Coordination Chemistry, High-Valent Salen Complexes as a Key to Investigate Mechanistic Aspects of Asymmetric Oxidation Catalysts and Metalloenzymes, Kurahashi Takuya; Fujii Hiroshi, In order to garner in-depth understanding of oxidation catalysis by salen complexes, we investigated the conformation, electronic structure and reactivity of high-valent salen complexes. We herein show that the conformation of a chiral manganese salen complex (Jacobsen's complex) is critically dependent on the oxidation state of the manganese ion and the external axial ligands that coordinate to the manganese ion, in relevance to asymmetric reactions. We also show that the reaction of a manganese(III) salen complex with m-chloroperoxybenzoic acid, an oxidant utilized for enantioselective epoxidation, generates a mixture of manganese(IV)-oxo and manganese(IV)-hydroxo species at –80°C. In contrast, the reaction of an iron(III) salen complex with m-chloroperoxybenzoic acid at –80°C generates a ligand radical complex with an iron(III) ion. The difference of electronic structures might be related to the fact that a manganese salen complex is a superior epoxidation catalyst than an iron salen complex. We also describe a model study for protocatechuate 3,4-dioxygenase using an iron(III) salen complex with sterically-hindered mesityl groups., 2011, 57, 57, 66, 10.4019/bjscc.57.57

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Unique Properties and Reactivity of High-Valent Manganese-Oxo versus Manganese-Hydroxo in the Salen Platform, Takuya Kurahashi; Akihiro Kikuchi; Yoshitsugu Shiro; Masahiko Hada; Hiroshi Fujii, To gain an understanding of oxidation reactions by Mn(III)(salen), a reaction of Mn(III)(salen) with m-chloroperoxybenzoic acid in the absence of a substrate is investigated. UV-vis, perpendicular- and parallel-mode electron paramagnetic resonance, and X-ray absorption spectroscopy show that the resulting solution contains Mn(IV)(salen)(O) as a major product and Mn(IV)(salen)(OH) as a minor product. Mn(IV)(salen)(O) readily reacts with 4-H-2,6-tert-Bu(2)C(6)H(2)OH (homolytic bond dissociation energy of an OH bond, BDE(OH) = 82.8 kcal mol(-1)), 4-CH(3)CO-2,6-tert-Bu(2)C(6)H(2)OH (BDE(OH) = 83.1 kcal mol(-1)), and 4-NC-2,6-tert-Bu(2)C(6)H(2)OH (BDE(OH) = 84.2 kcal mol(-1)) at 203 K, following second-order rate kinetics. Mn(IV)(salen)(OH) reacts with 4-CH(3)CO-2,6-tert-Bu(2)C(6)H(2)OH (BDE(OH) = 83.1 kcal mol(-1)) much more slowly under identical conditions than Mn(IV)(salen)(O) and does not react with 4-NC-2,6-tert-Bu(2)C(6)H(2)OH (BDE(OH) = 84.2 kcal mol(-1), suggesting that the thermodynamic hydrogen-atom-abstracting ability of Mn(IV)(salen)(OH) is about 83 kcal mol(-1). The rate constant for reactions of Mn(IV)(salen)(OH) with phenols is not dependent on the concentration of phenols, suggesting that Mn(IV)(salen)(OH) might bind phenols prior to the rate-limiting oxidation reactions. Quantum chemical calculations are carried out for Mn(IV)(salen)(O) and Mn(IV)(salen)(OH), both of which well reproduce the extended X-ray absorption fine structures as well as the electronic configurations. It is also indicated that protonation of Mn(IV)(salen)(OH) induces a drastic electronic structural change from manganese(IV) phenolate to a manganese(III) phenoxyl radical, which is also consistent with the experimental observation., Jul. 2010, 49, 14, 6664, 6672, Scientific journal, 10.1021/ic100673b

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• Not Refereed, CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, Resonance Raman Study of a High-valent Fe=O Porphyrin Complex as a Model for Peroxidase Compound II, Hirohito Ishimaru; Hiroshi Fujii; Takashi Ogura, Resonance Raman spectroscopy is applied to a Fe-IV oxo porphyrin with imidazolate as the axial ligand. The v(Fe=O) mode is observed at 792 cm(-1), which is 23 cm(-1) lower than that of the analogous 1-methylimidazole complex and similar to that of horseradish peroxidase compound II (787 cm(-1)) at alkaline pH, for which presence of an anionic histidine was previously postulated. This study thus provides a useful model compound of horseradish peroxidase compound II., Apr. 2010, 39, 4, 332, 333, Scientific journal, 10.1246/cl.2010.332

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Direct Probing of Spin State Dynamics Coupled with Electronic and Structural Modifications by Picosecond Time-Resolved XAFS, Shunsuke Nozawa; Tokushi Sato; Matthieu Chollet; Kouhei Ichiyanagi; Ayana Tomita; Hiroshi Fujii; Shin-ichi Adachi; Shin-ya Koshihara, The first direct observation of the transient spin-state in a disordered magnetic system with time-resolved XAFS is reported. By observing the evolution of the Fe(II) 1s -3d transition, the spin crossover transition from the (1)A(1) low spin state to (5)T(2) high spin state has been directly observed on a picosecond time scale. Moreover, observation of the transient spin state with time-resolved XAFS allows for the investigation of the variations in the electronic state and molecular structure. This unique experimental technique probes the excited states involved in the ultrafast photoinduced reactions in disordered magnetic systems., Jan. 2010, 132, 1, 61, +, Scientific journal, 10.1021/ja907460b

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• Not Refereed, BIOCHEMISTRY, AMER CHEMICAL SOC, Paramagnetic C-13 and N-15 NMR Analyses of the Push and Pull Effects in Cytochrome c Peroxidase and Coprinus cinereus Peroxidase Variants: Functional Roles of Highly Conserved Amino Acids around Heme, Daisuke Nonaka; Hiroyuki Wariishi; Karen G. Welinder; Hiroshi Fujii, Paramagnetic C-13 and N-15 nuclear magnetic resonance (NMR) spectroscopy of heme-bound cyanide ((CN)-C-13-N-15) was applied to 11 cytochrome e peroxidase (UP) and Coprinus cinereus peroxidase (CIP) mutants to investigate contributions to the Push and Pull effects of conserved amino acids around heme. The C-13 and N-15 NMR data for the distal His and Arg mutants indicated that distal His is the key amino acid residue creating the strong pull effect and that distal Arg assists. The Mutation of distal Trp of CcP to Phe, the amino acid at this position in CIP, changed the push and pull effects so they resembled those of CIP, whereas the mutation of distal Pile of CIP to Trp changed this mutant to become CcP-like. The C-13 NMR shifts for the proximal Asp mutants clearly showed that the proximal Asp-His hydrogen bonding strengthens the push effect. However, even in the absence of a hydrogen bond, the push effect of proximal His in peroxidase is significantly stronger than in globins. Comparison of these NMR data with the Compound I formation rate constants and crystal Structures Of these mutants showed that (1) the base catalysis of the distal His is more critical for rapid compound I Formation than its acid catalysis, (2) the primary function of the distal Arg is to maintain the distal heme pocket in favor of rapid Compound I formation via hydrogen bonding, and (3) the push effect is the major contribution to the differential rates of compound I formation in wild-type peroxidases., Jan. 2010, 49, 1, 49, 57, Scientific journal, 10.1021/bi9017285

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Critical Role of External Axial Ligands in Chirality Amplification of trans-Cyclohexane-1,2-diamine in Salen Complexes, Takuya Kurahashi; Masahiko Hada; Hiroshi Fujii, A series of Mn(IV)(salen)(L)(2) complexes bearing different external axial ligands (L = Cl, NO(3), N(3), and OCH(2)CF(3)) from chiral salen ligands with trans-cyclohexane-1,2-diamine as a chiral scaffold are synthesized, to gain insight into conformational properties of metal salen complexes. X-ray crystal structures show that Mn(IV)(salen)(OCH(2)CF(3))(2) and Mn(IV)(salen)(N(3))(2) adopt a stepped conformation with one of two salicylidene rings pointing upward and the other pointing downward due to the bias from the trans-cyclohexane-1,2-diamine moiety, which is in clear contrast to a relatively planar solid-state conformation for Mn(IV)(salen)(Cl)(2). The CH(2)Cl(2) solution of Mn(IV)(salen)(L)(2) shows circular dichroism of increasing intensity in the order L = Cl < NO(3) << N(3) < OCH(2)CF(3), which indicates Mn(IV)(salen)(L)(2) adopts a solution conformation of an increasing chiral distortion in this order. Quantum-chemical calculations with a symmetry adapted cluster-configuration interaction method indicate that a stepped conformation exhibits more intense circular dichroism than a planar conformation. The present study clarifies an unexpected new finding that the external axial ligands (L) play a critical role in amplifying the chirality in trans-cyclohexane-1,2-diamine in Mn(IV)(salen)(L)(2) to facilitate the formation of a chirally distorted conformation, possibly a stepped conformation., Sep. 2009, 131, 34, 12394, 12405, Scientific journal, 10.1021/ja904635n

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Catalytic Reactivity of a Meso-N-Substituted Corrole and Evidence for a High-Valent Iron-Oxo Species, Amanda J. McGown; William D. Kerber; Hiroshi Fujii; David P. Goldberg, It is shown that an iron(III) meso-N-substituted corrole (TBP(8)Cz)Fe(III) (1) (TBP(8)CZ = octakis(4-tert-butylphenyl)corrolazinato), is a potent catalyst for the oxidation of alkenes in the presence of pentaflouroiodosylbenzene (C(6)F(5)IO) as oxidant. In the case of cyclohexene, complex 1 performs on a par with one of the best porphyrin catalysts ((TPPF(20))FeCl), exhibiting rapid turnover and a high selectivity for epoxide (CzFe(III)/C(6)F(5)IO/cyclohexene (1:100:1000) in CH(2)Cl(2)/CH(3)OH (3:1 v:v) gives 33 turnovers of epoxide.in <2 min). Reaction rates for 1 are greatly enhanced compared to other Fe or Mn corroles under similar catalytic conditions, consistent with an increase in the electrophilicity of a high-valent iron-oxo intermediate induced by meso-N substitution. Reaction of dark-green 1 (lambda(max) = 440, 611, 747 nm) under single-turnover-ike conditions at -78 degrees C leads to the formation of a new dark-brown species (2) (lambda(max) = 396, 732, 843 nm). The Fe(III) complex 1 is restored upon the addition of 2 equiv of ferrocene to 2, or by the addition of 1 equiv of PPh(3), which concomitantly yields OPPh(3). In addition, complex 2 reacts with excess cyclohexene at -42 degrees C to give 1. Complex 2 was also characterized by EPR spectroscopy, and all of the data are consistent with 2 being an antiferromagnetically coupled iron(IV)-oxo pi-cation-radical complex. Rapid-mixing stopped-flow UV-vis studies show that the low-temperature complex 2 is generated as a short-lived intermediate at room temperature., Jun. 2009, 131, 23, 8040, 8048, Scientific journal, 10.1021/ja809183z

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Effect of Imidazole and Phenolate Axial Ligands on the Electronic Structure and Reactivity of Oxoiron(IV) Porphyrin pi-Cation Radical Complexes: Drastic Increase in Oxo-Transfer and Hydrogen Abstraction Reactivities, Akihiro Takahashi; Takuya Kurahashi; Hiroshi Fujii, To study the effect of axial ligands on the electronic structure and reactivity of compound I of peroxidases and catalases, oxoiron(IV) porphyrin pi-cation radical complexes with imidazole, 2-methylimidazole, 4(5)-methylimidazole, and 3-fluoro-4-nitrophenolate as the axial ligands were prepared by ozone oxidation of iron(III) complexes of 5,10,15,20-tetramesitylporphyrin (TMP) and 2,7,12,17-tetramethyl-3,8,13,18-tetramesitylporphyrin (TMTMP). These complexes were fully characterized by absorption, H-1, H-2, and F-19 NMR, electron paramagnetic resonance (EPR), and electrospray ionization mass spectrometry (ESI-MS) spectroscopy. The characteristic absorption peak of compound I at approximately 650 nm was found to be a good marker for estimation of the electron donor effect from the axial ligand. The axial ligand effect did not change the porphyrin pi-cation radical state, the a(2u) state of the TMP complexes, or the a,, radical state of both the TMTMP complexes and compound 1. The ferryl iron and porphyrin pi-cation radical spins were effectively transferred into the axial ligands for the a2u complexes but not for the a,, complexes. Most importantly, the reactivity of the oxoiron(IV) porphyrin pi-cation radical complex was drastically increased by the imidazole and phenolate axial ligands. The reaction rate for cyclooctene epoxidation was increased 100- to 400-fold with axial coordination of imidazoles and phenolate. A similar increase was also observed for the oxidation of 1,4-cyclohexadiene, N, N-dimethyl-p-nitroaniline and hydrogen peroxide. These results suggest extreme enhancement of the reactivity of compound I by the axial ligand in heme enzymes. The functional role of axial ligands on the compound I in heme enzymes is discussed., Mar. 2009, 48, 6, 2614, 2625, Scientific journal, 10.1021/ic802123m

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• Not Refereed, BIOCHEMISTRY, AMER CHEMICAL SOC, Paramagnetic C-13 and N-15 NMR Analyses of Cyanide- ((CN)-C-13-N-15-) Ligated Ferric Peroxidases: The Push Effect, Not Pull Effect, Modulates the Compound I Formation Rate, Daisuke Nonaka; Hiroyuki Wariishi; Hiroshi Fujii, Paramagnetic C-13 and N-15 NMR spectroscopy of home-bound cyanide ((CN)-C-13-N-15) was utilized to quantitatively distinguish the electron donor effect (the push effect) from the proximal histidine and hydrogen-bonding effect (the pull effect) from the distal amino acid residues in cytochrome c peroxidase (CcP), ascorbate peroxidase (APX), lignin peroxidase (LiP), and manganese peroxidase (MnP). Paramagnetic C-13 NMR signals of heme-bound (CN)-C-13-N-15 of these peroxidases were observed in a wide range, -3501 ppm (CcP), -3563 ppm (APX), -3823 ppm (MnP), and -3826 ppm (LiP), while paramagnetic N-15 NMR signals of those were detected in a narrow range, 574 ppm (ARP), 605 ppm (CcP), 626 ppm (LiP), and 654 ppm (MnP). Detailed analysis, combined with the previous results for horseradish peroxidase and Arthromyces ramosus peroxidase, indicated that the push effect is quite different among these peroxidases while the pull effect is similar. More importantly, a strong correlation between the C-13 NMR shift (the push effect) and the compound I: formation rate was observed, indicating that the push effect causes a variation in the compound I formation rate. Comparison of the C-13 and N-15 NMR results of these peroxidases with their crystal structures suggests that the orientation of the proximal imidazole plane to the heme N-Fe-N axis controls the push effect and the compound I formation rate of peroxidase., Feb. 2009, 48, 5, 898, 905, Scientific journal, 10.1021/bi802030a

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• Not Refereed, JOURNAL OF SYNCHROTRON RADIATION, WILEY-BLACKWELL PUBLISHING, INC, Capturing molecular structural dynamics by 100 ps time-resolved X-ray absorption spectroscopy, Tokushi Sato; Shunsuke Nozawa; Kohei Ichiyanagi; Ayana Tomita; Matthieu Chollet; Hirohiko Ichikawa; Hiroshi Fujii; Shin-ichi Adachi; Shin-ya Koshihara, An experimental set-up for time-resolved X-ray absorption spectroscopy with 100 ps time resolution at beamline NW14A at the Photon Factory Advanced Ring is presented. The X-ray positional active feedback to crystals in a monochromator combined with a figure-of-merit scan of the laser beam position has been utilized as an essential tool to stabilize the spatial overlap of the X-ray and laser beams at the sample position. As a typical example, a time-resolved XAFS measurement of a photo-induced spin crossover reaction of the tris(1,10-phenanthrorine)iron(II) complex in water is presented., Jan. 2009, 16, 110, 115, Scientific journal, 10.1107/S0909049508034596

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• Not Refereed, CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, ENDOR Study of Oxoiron(IV) Porphyrin pi-Cation Radical Complexes as Models for Compound I of Heme Enzymes, Akihiro Takahashi; Yasunori Ohba; Seigo Yamauchi; Hiroshi Fujii, Electron nuclear double resonance (ENDOR) spectroscopy of oxoiron(IV) porphyrin pi-cation radical complexes with pyrrole beta-substituted porphyrins is reported. Hyperfine coupling constants (A(H)) of the pyrrole beta-methyl groups were determined. Comparison of the A H values with those of compound I of peroxidase and catalase indicated the a(Iu) porphyrin pi-cation radical states of these compound I., Jan. 2009, 38, 1, 68, 69, Scientific journal, 10.1246/cl.2009.68

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• Refereed, LXIII YAMADA CONFERENCE ON PHOTO-INDUCED PHASE TRANSITION AND COOPERATIVE PHENOMENA (PIPT3), IOP PUBLISHING LTD, 100-picosecond Time-resolved X-ray Absorption Fine Structure of Fe-II(1,10-phenanthroline)(3), Tokushi Sato; Shunsuke Nozawa; Kouhei Ichiyanagi; Ayana Tomita; Hirohiko Ichikawa; Matthieu Chollet; Hiroshi Fujii; Shin-ichi Adachi; Shin-ya Koshihara, Studying photo-induced molecular dynamics in liquid with sub-nanosecond time-resolution and sub-Angstrom spatial resolution gives information for understanding fundamental chemical process in the photo-induced cooperative phenomena of molecular systems and also for developing new materials and devices. Here, we present time-resolved Xray absorption fine structure on the spin-crossover complex Fe-II tris-(1,10-phenanthroline) dissolved in aqueous solution. We utilized femtosecond laser at 400nm pulse for excitation and 100ps X-ray pulse for probe., 2009, 148, 012035, International conference proceedings, 10.1088/1742-6596/148/1/012035

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Chiral distortion in a Mn(IV)(salen)(N(3))(2) derived from Jacobsen's catalyst as a possible conformation model for its enantioselective reactions, Takuya Kurahashi; Hiroshi Fujii, The Mn(IV)(salen)(N(3))(2) complex (3) from Jacobsen's catalyst is synthesized, and the X-ray crystal structures of 3 as well as the starting Mn(III)(salen)(N(3))(CH(3)OH) complex (2) are determined in order to investigate the conformation of the high-valent Mn(IV)(salen) molecule in comparison with that of Mn(III)(salen). The asymmetric unit of the crystal of 3 contains four complexes, all of which adopt a nonplanar stepped conformation effectively distorted by the chirality of the diimine bridge. The asymmetric unit of 2 also contains four complexes. Two of them show a stepped conformation of a lesser degree, but the other two adopt a bowl-shaped conformation. Comparison of the structural parameters shows that the Mn center in 3 is coordinated from both sides by two external axial N(3) ligands with significantly shorter bond lengths, which could induce greater preference for the stepped conformation in 3. The CH(3)CN solution of 3 shows circular dichroism with a significantly strong band at 275 nm as compared to 2, suggesting that 3 may adopt a more chirally distorted conformation also in solution. The circular dichroism spectrum of 3 is slightly altered with isodichroic points from 298 to 253 K and shows no further change at temperatures lower than 253 K, suggesting that the solution of 3 contains an equilibrium between two conformers, where a low-energy conformer with more chiral distortion is predominantly favored even at room temperature. Complexes 2 and 3 are thoroughly characterized using various techniques including cyclic voltammetry, magnetic susceptibility, UV-vis, electron paramagnetic resonance, (1)H NMR, infrared spectroscopy, and electrospray ionization mass spectrometry., Sep. 2008, 47, 17, 7556, 7567, Scientific journal, 10.1021/ic800443q

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Effect of a tridentate ligand on the structure, electronic structure, and reactivity of the copper(I) nitrite complex: Role of the conserved three-histidine ligand environment of the type-2 copper site in copper-containing nitrite reductases, Masato Kujime; Chiemi Izumi; Masaaki Tomura; Masahiko Hada; Hiroshi Fujii, It is postulated that the copper(I) nitrite complex is a key reaction intermediate of copper containing nitrite reductases (Cu-NiRs), which catalyze the reduction of nitrite to nitric oxide (NO) gas in bacterial clenitrification. To investigate the structure-function relationship of Cu-NiR, we prepared five new copper(I) nitrite complexes with sterically hindered tris(4-imidazolyl)carbinois [Et-TIC = tris(1-methyl-2-ethyl-4-imidazolyl)carbinol and iPr-TIC = tris(1-methyl-2-isopropyl-4-imidazolyl)carbinol] or tris(1-pyrazolyl)methanes [Me-TPM = tris(3,5-dimethyl-1-pyrazolyl) methane; Et-TPM = tris(3,5-diethyl-1-pyrazolyl) methane; and iPr-TPM = tris(3,5-diisopropyl-1-pyrazolyl) methane]. The X-ray crystal structures of all of these copper(II) nitrite complexes were mononuclear eta(1)-N-bound nitrite complexes with a distorted tetrahedral geometry. The electronic structures of the complexes were investigated by absorption, magnetic circular dichroism (MCD), NMR, and vibrational spectroscopy. All of these complexes are good functional models of Cu-NiR that form NO and copper(II) acetate complexes well from reactions with acetic acid under anaerobic conditions. A comparison of the reactivity of these complexes, including previously reported (iPr-TACN)Cu(NO(2)) [iPr-TACN = 1,4,7-triisopropyl-1,4,7-triazacyclononane], clearly shows the drastic effects of the tridentate ligand on Cu-NiR activity. The copper(I) nitrite complex with the Et-TIC ligand, which is similar to the highly conserved three-histidine ((HiS)(3)) ligand environment in the catalytic site of Cu-NiR, had the highest Cu-NiR activity. This result suggests that the (HiS)(3) ligand environment is essential for acceleration of the Cu-NiR reaction. The highest Cu-NiR activity for the Et-TIC complex can be explained by the structural and spectroscopic characterizations and the molecular orbital calculations presented in this paper. Based on these results, the functional role of the (HiS)(3) ligand environment in Cu-NiR is discussed., May 2008, 130, 19, 6088, 6098, Scientific journal, 10.1021/ja075575b

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Transient intermediates from Mn(salen) with sterically hindered mesityl groups: Interconversion between Mn-IV-phenolate and Mn-III-phenoxyl radicals as an origin for unique reactivity, Takuya Kurahashi; Akihiro Kikuchi; Takehiko Tosha; Yoshitsugu Shiro; Teizo Kitagawa; Hiroshi Fujii, In order to reveal structure-reactivity relationships for the high catalytic activity of the epoxidation catalyst Mn(salen), transient intermediates are investigated. Steric hindrance incorporated to the salen ligand enables highly selective generation of three related intermediates, O = Mn-IV(salen), HO-Mn-IV(salen), and H2O-Mn-III(salen(+center dot)), each of which is thoroughly characterized using various spectroscopic techniques including UV-vis, electron paramagnetic resonance, resonance Raman, electrospray ionization mass spectrometry, H-2 NMR, and X-ray absorption spectroscopy. These intermediates are all one-electron oxidized from the starting Mn-III(salen) precursor but differ only in the degree of protonation. However, structural and electronic features are strikingly different: The Mn-O bond length of HO-Mn-IV(salen) (1.83 angstrom) is considerably longer than that of O = Mn-IV(salen) (1.58 angstrom); the electronic configuration of H2O-Mn-III(salen(+center dot)) is Mn-III-phenoxyl radical, while those of O = Mn-IV(salen) and HO-Mn-IV(salen) are Mn-IV-phenolate. Among O = Mn-IV(salen), HO-Mn-IV(salen), and H2O-Mn-III(salen(+center dot)), only the O = Mn-IV(salen) can transfer oxygen to phosphine and sulfide substrates, as well as abstract hydrogen from weak C-H bonds, although the oxidizing power is not enough to epoxiclize olefins. The high activity of Mn(salen) is a direct consequence of the favored formation of the reactive O = Mn-IV(salen) state., Mar. 2008, 47, 5, 1674, 1686, Scientific journal, 10.1021/ic702061y

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• Not Refereed, 固体物理, 2. 金属酵素の反応中間体の電子状態・構造解析, 藤井 浩; 城 宜嗣, 2008, 43, 11, 7, 18
• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Activation parameters for cyclohexene oxygenation by an oxoiron(IV) porphyrin pi-cation radical complex: Entropy control of an allylic hydroxylation reaction, Akihiro Takahashi; Takuya Kurahashi; Hiroshi Fujii, Activation parameters for epoxidation and allylic hydroxylation reactions of cyclohexene with (FeO)-O-IV(TMP)Cl center dot+ (1) were determined. Within the experimental temperature range, the epoxidation reaction was enthalpy-controlled (i.e., Delta H-double dagger > -T Delta S-double dagger), while the allylic hydroxylation reaction was entropy-controlled (i.e., -T Delta S-double dagger > Delta H-double dagger). An unexpectedly large contribution of the entropy term for the allylic hydroxylation reaction indicated that the free energy of activation, Delta G(double dagger), rather than the activation energy, E-a, should be used to discuss the reaction mechanism and chemoselectivity. The results of this study bring caution to previous density functional theory studies, in which the reaction mechanism and chemoselectivity are evaluated from calculated E-a., Aug. 2007, 46, 16, 6227, 6229, Scientific journal, 10.1021/ic7009379

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Cu-63 NMR spectroscopy of Copper(I) complexes with various tridentate ligands: CO as a useful Cu-63 NMR probe for sharpening Cu-63 NMR signals and analyzing the electronic donor effect of a ligand, Masato Kujime; Takuya Kurahashi; Masaaki Tomura; Hiroshi Fujii, Cu-63 NMR spectroscopic studies of copper(I) complexes with various N-donor tridentate ligands are reported. As has been previously reported for most copper(I) complexes, Cu-63 NMR signals, when acetonitrile is coordinated to copper(I) complexes of these tridentate ligands, are broad or undetectable. However, when CO is bound to tridentate copper(I) complexes, the Cu-63 NMR signals become much sharper and show a large downfield shift compared to those for the corresponding acetonitrile complexes. Temperature dependence of Cu-63 NMR signals for these copper(I) complexes show that a quadrupole relaxation process is much more significant to their Cu-63 NMR line widths than a ligand exchange process. Therefore, an electronic effect of the copper bound CO makes the Cu-63 NMR signal sharp and easily detected. The large downfield shift for the copper(I) carbonyl complex can be explained by a paramagnetic shielding effect induced by the copper bound CO, which amplifies small structural and electronic changes that occur around the copper ion to be easily detected in their Cu-63 NMR shifts. This is evidenced by the correlation between the Cu-63 NMR shifts for the copper(I) carbonyl complexes and their nu(CO) values. Furthermore, the Cu-63 NMR shifts for copper(I) carbonyl complexes with imino-type tridentate ligands show a different correlation line with those for amino-type tridentate ligands. On the other hand, C-13 NMR shifts for the copper bound (CO)-C-13 for these copper(I) carbonyl complexes do not correlate with the nu(CO) values. The X-ray crystal structures of these copper(I) carbonyl complexes do not show any evidence of a significant structural change around the Cu-CO moiety. The findings herein indicate that CO complexation makes Cu-63 NMR spectroscopy much more useful for Cu(I) chemistry., Jan. 2007, 46, 2, 541, 551, Scientific journal, 10.1021/ic060745r

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Trigonal-bipyramidal geometry induced by an external water ligand in a sterically hindered iron salen complex, related to the active site of protocatechuate 3,4-dioxygenase, Takuya Kurahashi; Kenji Oda; Manabu Sugimoto; Takashi Ogura; Hiroshi Fujii, A unique distorted trigonal-bipyramidal geometry observed for the non-heme iron center in protocatechuate 3,4dioxygenase (3,4-PCD) was carefully examined utilizing a sterically hindered iron salen complex, which well reproduces the endogenous His(2)Tyr(2) donor set with water as an external ligand. X-ray crystal structures of a series of iron model complexes containing bis(3,5-dimesitylsalicylidene)-1,2-dimesitylethylenediamine indicate that a distorted trigonal-bipyramidal geometry is achieved upon binding of water as an external ligand. The extent of a structural change of the iron center from a preferred square-pyramidal to a distorted trigonal-bipyramidal geometry varies with the external ligand that is bound in the order Cl << EtO < H2O, which is consistent with the spectrochemical series. The distortion in the model system is not due to steric repulsions but electronic interactions between the external ligand and the iron center, as evidenced from the X-ray crystal structures of another series of iron model complexes with a less-hindered bis(3-xylylsalicylidene)-1,2-dimesitylethylenediamine ligand, as well as by density functional theory calculations. Further spectroscopic investigations indicate that a unique distorted trigonal-bipyramidal geometry is indeed maintained even in solution. The present model study provides a new viewpoint that a unique distorted trigonal-bipyramidal iron site might not be preorganized by a 3,4-PCD protein but could be electronically induced upon the binding of an external hydroxide ligand to the iron(III) center. The structural change induced by the external water ligand is also discussed in relation to the reaction mechanism of 3,4-PCD., Sep. 2006, 45, 19, 7709, 7721, Scientific journal, 10.1021/ic060650p

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, C-13 and N-15 NMR studies of iron-bound cyanides of heme proteins and related model complexes: Sensitive probe for detecting hydrogen-bonding interactions at the proximal and distal sides, Hiroshi Fujii; Tadashi Yoshida, Studies of the C-13 and N-15 NMR paramagnetic shifts of the iron-bound cyanides in the ferric cyanide forms of various heme proteins containing the proximal histidine and related model complexes are reported. The paramagnetic shifts of the C-13 and N-15 NMR signals of the iron-bound cyanide are not significantly affected by the substitution of the porphyrin side chains. On the other hand, the paramagnetic shifts of both the C-13 and N-15 NMR signals decrease with an increase in the donor effect of the proximal ligand, and the C-13 NMR signal is more sensitive to a modification of the donor effect of the proximal ligand than the N-15 NMR signal. With the tilt of the iron-imidazole bond, the paramagnetic shift of the C-13 NMR signal increases, whereas that of the N-15 NMR signal decreases. The hydrogen-bonding interaction of the iron-bound cyanide with a solvent decreases the paramagnetic shift of both C-13 and N-15 NMR signals, and the effect is more pronounced for the N-15 NMR signal. Data on the C-13 and N-15 NMR signals of iron-bound cyanide for various heme proteins are also reported and analyzed in detail. Substantial differences in the C-13 and N-15 NMR shifts for the heme proteins can be explained on the basis of the results for the model complexes and structures around the heme in the heme proteins. The findings herein show that the paramagnetic shift of the C-13 NMR signal of the iron-bound cyanide is a good probe to estimate the donor effect of the proximal imidazole and that the ratio of N-15/C-13 NMR shifts allows the hydrogen-bonding interaction on the distal side to be estimated., Aug. 2006, 45, 17, 6816, 6827, Scientific journal, 10.1021/ic0607383

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• Not Refereed, JOURNAL OF INORGANIC BIOCHEMISTRY, ELSEVIER SCIENCE INC, O-17 NMR study of oxo metalloporphyrin complexes: Correlation with electronic structure of M=O moiety, H Fujii; T Kurahashi; T Tosha; T Yoshimura; T Kitagawa, O-17 NMR spectroscopy of oxo ligand of oxo metalloporphyrin can be considered as an excellent means to derive information about structure, electronic state, and reactivity of the metal bound oxo ligand. To show the Utility Of O-17 NMR spectroscopy of oxo ligand of oxo metalloporphyrin. O-17 NMR spectra of oxo ligands of dioxo ruthenium(VI), oxo chromium(IV), and oxo titanium(IV) porphyrins are measured. For all oxo metalloporphyrins, well-resolved O-17 NMR signals are detected in far high frequency region. The O-17 NMR signal of the metal bound oxo ligand shifts high frequency in order of Ru(VI) < Ti(IV) < Cr(IV), thus the O-17 NMR chemical shift does not directly correlate with the oxo-transfer reactivity, Ti(IV) < Cr(IV) < Ru(VI). On the other hand, the O-17 NMR shift of oxo ligand correlates with the bond strength of metal-oxo bond. This suggests that the O-17 NMR signal of metal bound oxo ligand is a sensitive probe to study the nature of metal-oxo bond in oxo metalloporphyrin. The effect of the electron-withdrawing meso-substituent on the O-17 NMR shift of the oxo ligand is also investigated. With increase in the electron-withdrawing effect of the meso-substituent, the O-17 NMR signal of the oxo ligand of oxo chromium(IV) porphyrin shifts high frequency while that or dioxo ruthenium(VI) porphyrin hardly change resonance position. The changes in metal-oxo bonds induced by the electron-withdrawing meso-substituent are discussed on the basis of the O-17 NMR shifts, the strengths of the metal-oxo bonds, and the oxo-transfer reaction rates. (c) 2006 Elsevier Inc. All rights reserved., Apr. 2006, 100, 4, 533, 541, Scientific journal, 10.1016/j.jinorgbio.2006.01.009

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• Not Refereed, BIOCHEMISTRY, AMER CHEMICAL SOC, Roles of the herne distal residues of FixL in O-2 sensing: A single convergent structure of the heme moiety is relevant to the downregulation of kinase activity, A Tanaka; H Nakamura; Y Shiro; H Fujii, FixL is a heme-based O-2 sensor, in which the autophosphorylation is regulated by the binding of exogenous ligands such as O-2 and CN-. In this study, mutants of the heme distal Arg200, Arg208, Ile2O9, Ile210, and Arg214 residues of SmFixL were characterized biochemically and physicochemically, because it has been suggested that they are significant residues in ligand-linked kinase regulation. Measurements of the autoxidation rate, affinities, and kinetics of ligand binding revealed that all of the above residues are involved in stabilization of the O-2-heme complex of FixL. However, Arg214 was found to be the only residue that is directly relevant to the ligand-dependent regulation of kinase activity. Although the wild type and R214K and R214Q mutants exhibited normal kinase regulation, R214A, R214M, R214H, and R214Y did not. C-13 and N-15 NMR analyses for (CN-)-C-13-N-15 bound to the truncated heme domains of the Arg214 mutants indicated that, in the wild type and the foregoing two mutants, the heme moiety is present in a single conformation, but in the latter four, the conformations fluctuate possibly because of the lack of an interaction between the iron-bound ligand and residue 214. It is likely that such a rigid conformation of the ligand-bound form is important for the downregulation of histidine kinase activity. Furthermore, a comparison of the NMR data between the wild type and R214K and R214Q mutants suggests that a strong electrostatic interaction between residue 214 and the iron-bound ligand is not necessarily required for the single convergent structure and eventually for the downregulation of FixL., Feb. 2006, 45, 8, 2515, 2523, Scientific journal, 10.1021/bi051989a

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-BLACKWELL, Spectroscopic characterization of reaction intermediates in a model for copper nitrite reductase, M Kujime; H Fujii, 2006, 45, 7, 1089, 1092, Scientific journal, 10.1002/anie.200503555

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• Not Refereed, JOURNAL OF BIOLOGICAL CHEMISTRY, AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, O-2- and H2O2-dependent verdoheme degradation by heme oxygenase - Reaction mechanisms and potential physiological roles of the dual pathway degradation, T Matsui; A Nakajima; H Fujii; KM Matera; CT Migita; T Yoshida; M Ikeda-Saito, Heme oxygenase (HO) catalyzes the catabolism of heme to biliverdin, CO, and a free iron through three successive oxygenation steps. The third oxygenation, oxidative degradation of verdoheme to biliverdin, has been the least understood step despite its importance in regulating HO activity. We have examined in detail the degradation of a synthetic verdoheme IX alpha complexed with rat HO-1. Our findings include: 1) HO degrades verdoheme through a dual pathway using either O-2 or H2O2; 2) the verdoheme reactivity with O-2 is the lowest among the three O-2 reactions in the HO catalysis, and the newly found H2O2 pathway is similar to 40-fold faster than the O-2-dependent verdoheme degradation; 3) both reactions are initiated by the binding of O-2 or H2O2 to allow the first direct observation of degradation intermediates of verdoheme; and 4) Asp(140) in HO-1 is critical for the verdoheme degradation regardless of the oxygen source. On the basis of these findings, we propose that the HO enzyme activates O-2 and H2O2 on the verdoheme iron with the aid of a nearby water molecule linked with Asp140. These mechanisms are similar to the well established mechanism of the first oxygenation, meso-hydroxylation of heme, and thus, HO can utilize a common architecture to promote the first and third oxygenation steps of the heme catabolism. In addition, our results infer the possible involvement of the H2O2-dependent verdoheme degradation in vivo, and potential roles of the dual pathway reaction of HO against oxidative stress are proposed., Nov. 2005, 280, 44, 36833, 36840, Scientific journal, 10.1074/jbc.M503529200

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Oxidizing intermediates from the sterically hindered iron salen complexes related to the oxygen activation by nonheme iron enzymes, T Kurahashi; Y Kobayashi; S Nagatomo; T Tosha; T Kitagawa; H Fujii, Oxidizing intermediates are generated from nonheme iron(III) complexes to investigate the electronic structure and the reactivity, in comparison with the oxoiron(IV) porphyrin pi-cation radical (compound 1) as a heme enzyme model. Sterically hindered iron salen complexes, bearing a fifth ligand Cl (1), OH2 (2), OEt (3), and OH (4), are oxidized both electrochemically and chemically. Stepwise one-electron oxidation of 1 and 2 generates iron(Ill)mono- and diphenoxyl radicals, as revealed by detailed spectroscopic investigations, including UV-vis, EPR, Mossbauer, resonance Raman, and ESIMS spectroscopies. In contrast to the oxoiron(IV) formation from the hydroxoiron(III) porphyrin upon one-electron oxidation, the hydroxo complex 4 does not generate oxoiron(IV) species. Reaction of 2 with mCPBA also results in the formation of the iron(Ill)-phenoxyl radical. One-electron oxidation of 3 leads to oxidative degradation of the fifth DO ligand to liberate acetaldehyde even at 203 K. The iron(Ill)phenoxyl radical shows high reactivity for alcoxide on iron(III) but exhibits virtually no reactivity for alcohols including even benzyl alcohol without a base to remove an alcohol proton. This study explains unique properties of mononuclear nonheme enzymes with Tyr residues and also the poor epoxidation activity of Fe salen compared to Mn and Cr salen compounds., Oct. 2005, 44, 22, 8156, 8166, Scientific journal, 10.1021/ic051377e

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• Not Refereed, TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, Synthesis of sterically hindered tris(4-imidazolyl)carbinol ligands and their copper(I) complexes related to metalloenzymes, M Kujime; H Fujii, Tris(4-imidazolyl)carbinol, which has close coordination environment to the active site of metalloenzymes, has not been utilized as a biomimetic ligand because of its instability. We have synthesized stable tris(4-imidazolyl)carbinol derivatives having a methyl group as the NH protective group and a bulky substituent on the imidazole ring for stabilizing reactive species bound to the metal center. These ligands provide stable monomeric copper(l) complexes whose coordination environment are very close to the active site of metalloenzymes. (c) 2005 Elsevier Ltd. All rights reserved., Apr. 2005, 46, 16, 2809, 2812, Scientific journal, 10.1016/j.tetlet.2005.02.122

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Essential amino acid residues controlling the unique regioselectivity of heme oxygenase in Pseudomonas aeruginosa, H Fujii; XH Zhang; T Yoshida, Apr. 2004, 126, 14, 4466, 4467, Scientific journal, 10.1021/ja031791l

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, A superoxo-ferrous state in a reduced oxy-ferrous hemoprotein and model compounds, R Davydov; JD Satterlee; H Fujii; A Sauer-Masarwa; DH Busch; BM Hoffman, Cryoreduction of the [FeO2](6) (n = 6 is the number of electrons in 3d orbitals on Fe and pi* orbitals on O-2) dioxygen-bound ferroheme through gamma irradiation at 77 K generates an [FeO2](7) reduced oxy-heme. Numerous investigations have examined [FeO2](7) centers that have been characterized as peroxo-ferric centers, denoted [FeO2](per)(7), in which a ferriheme binds a dianionic peroxo-ligand. The generation of such an intermediate can be understood heuristically if the [FeO2](6) parent is viewed as a superoxo-ferric center and the injected electron localizes on the O-O moiety. We here report EPR/ENDOR experiments which show quite different properties for the [FeO2](7) centers produced by cryoreduction of monomeric oxy-hemoglobin (oxy-GMH3) from Glycera dibranchiata, which is unlike mammalian "globins" in having a leucine in place of the distal histidine; of frozen aprotic solutions of oxy-ferrous octaethyl porphyrin; and of the oxy-ferrous complex of the heme model, cyclidene. These [FeO2](7) centers are characterized as "superoxo-ferrous" centers ([FeO2](sup)(7)), With nearly unit spin density localized on a superoxo moiety which is end-on coordinated to a low-spin ferrous ion. This assignment is based on their g tensors and O-17 hyperfine couplings, which are characteristic of the superoxide ion coordinated to a diamagnetic metal ion, and on the absence of detectable ENDOR signals either from the in-plane N-14 ligands or from an exchangeable H-bond proton. Such a center would arise if the electron that adds to the [FeO2](6) superoxo-ferric parent localizes on the Fe ion, to make a superoxo-ferrous moiety. Upon annealing to T > 150 K, the [FeO2](sup)(7) species converts to peroxo/hydroperoxo-ferric ([FeO2H](7)) intermediates. These experiments suggest that the primary reduction product is [FeO2](sup)(7) and that the internal redox transition to [FeO2](per)(7)/[FeO2H](7) states is driven at least in part by H-bonding/proton donation by the environment., Dec. 2003, 125, 52, 16340, 16346, Scientific journal, 10.1021/ja037037e

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Kinetic isotope effects on the rate-limiting step of heme oxygenase catalysis indicate concerted proton transfer/heme hydroxylation, R Davydov; T Matsui; H Fujii; M Ikeda-Saito; BM Hoffman, Dec. 2003, 125, 52, 16208, 16209, Scientific journal, 10.1021/ja038923s

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• Not Refereed, BIOCHEMISTRY, AMER CHEMICAL SOC, Stereo selectivity of each of the three steps of the heme oxygenase reaction: Hemin to meso-hydroxyhemin, meso-hydroxyhemin to verdoheme, and verdoheme to biliverdin, XH Zhang; H Fujii; KM Matera; CT Migita; DY Sun; M Sato; M Ikeda-Saito; T Yoshida, Heme oxygenase catalyzes the regiospecific oxidation of hemin to biliverdin IXalpha with concomitant liberation of CO and iron by three sequential monooxygenase reactions. The alpha-regioselectivity of heme oxygenase has been thought to result from the regioselective oxygenation of the heme alpha-meso position at the first step, which leads to the reaction pathway via meso-hydroxyheme IXalpha and verdoheme IXalpha intermediates. However, recent reports concerning heme oxygenase forming biliverdin isomers other than biliverdin IXalpha raise a question whether heme oxygenase can degrade meso-hydroxyhemin and isomers other than the alpha-isomers. In this paper, we investigated the stereoselectivity of each of the two reaction steps from meso-hydroxyhemin to verdoheme and verdoheme to biliverdin by using a truncated form of rat heme oxygenase-1 and the chemically synthesized four isomers of meso-hydroxyhemin and verdoheme. Heme oxygenase-1 converted all four isomers of meso-hydroxyhemin to the corresponding isomers of verdoheme. In contrast, only verdoheme IXalpha was converted to the corresponding biliverdin IXalpha. We conclude that the third step, but not the second, is stereoselective for the alpha-isomer substrate. The present findings on regioselectivities of the second and the third steps have been discussed on the basis of the oxygen activation mechanisms of these steps., Jun. 2003, 42, 24, 7418, 7426, Scientific journal, 10.1021/bi027173g

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, Preparation of artificial metalloenzymes by insertion of chromium(III) Schiff base complexes into apomyoglobin mutants, M Ohashi; T Koshiyama; T Ueno; M Yanase; H Fujii; Y Watanabe, 2003, 42, 9, 1005, +, Scientific journal, 10.1002/anie.200390256

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• Refereed, PARAMAGNETIC RESONANCE OF METALLOBIOMOLECULES, AMER CHEMICAL SOC, EPR characterization of the heme oxygenase reaction intermediates and its implication for the catalytic mechanism, M Ikeda-Saito; H Fujii, Heme oxygenase (HO) catalyzes the regiospecific degradation of heme to biliverdin by using three O-2 molecules and seven electrons. The enzyme binds one equivalent of heme to form the heme complex, and electron donation initiates the three stepwise oxygenase reactions through the two novel heme derivatives, alpha-hydroxyheme and verdoheme, during which CO and free Fe are also produced. EPR has been used to study electronic and coordination structures of the HO catalytic intermediates, including the ferric hydroperoxo active species generated by one-electron reduction of the ferrous oxy form. A combination of the novel characteristics of the reaction intermediates and the protein environment are responsible for the unique HO enzyme catalytic mechanism., 2003, 858, 97, 112, Scientific journal
• Refereed, PHYSICS LETTERS B, ELSEVIER SCIENCE BV, Superpenetration of a high energy Q(Q)over-bar bound state through random color fields, H Fujii; T Matsui, The transmission amplitude of a color dipole through a random external color field is computed in the eikonal approximation in order to study the absorption of high energy quarkonium by nuclear target. It is shown that the internal color state of the dipole becomes randomized and all possible color states are eventually equi-partitioned, while the probability of finding a color singlet bound state attenuates not exponentially, but inversely proportional to the distance L of the random field zone which the dipole has traveled. (C) 2002 Elsevier Science B.V. All rights reserved., Oct. 2002, 545, 1-2, 82, 90, Scientific journal
• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, C-13 NMR signal detection of iron-bound cyanide ions in ferric cyanide complexes of heme proteins, H Fujii, May 2002, 124, 21, 5936, 5937, Scientific journal, 10.1021/ja025737y

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• Not Refereed, COORDINATION CHEMISTRY REVIEWS, ELSEVIER SCIENCE SA, Electronic structure and reactivity of high-valent oxo iron porphyrins, H Fujii, High valent oxo iron porphyrins have been prepared and characterized as models for compounds-I and compounds-II in heme enzymes. In this review, we survey studies of high valent oxo iron porphyrin complexes. Spectroscopic properties and reactivities of oxo iron(IV) porphyrin pi-cation radical complexes are summarized. Electron-withdrawing effects of meso-substituents and pyrrole beta-substituents on the electronic structure of oxo iron(IV) porphyrin pi-cation radicals are discussed. The effect of the axial ligand is also reviewed. Isoelectronic forms of oxo iron(IV) porphyrin pi-cation radical are reviewed. We have summarized the synthesis and characterization of oxo iron(IV) porphyrins as models for compounds-II. (C) 2002 Elsevier Science B.V. All rights reserved., Mar. 2002, 226, 1-2, 51, 60, Scientific journal, 10.1016/S0010-8545(01)00441-6

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Catalytic mechanism of heme oxygenase through EPR and ENDOR of cryoreduced oxy-heme oxygenase and its Asp 140 mutants, R Davydov; Kofman, V; H Fujii; T Yoshida; M Ikeda-Saito; BM Hoffman, Heme oxygenase (HO) catalyzes the O-2- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, and CO through a process in which the heme participates both as a prosthetic group and as a substrate. In the present study, we have generated a detailed reaction cycle for the first monooxygenation step of HO catalysis, conversion of the heme to alpha-meso-hydroxyheme. We employed EPR (using both O-16(2) and O-17(2)) and H-1, N-14 ENDOR spectroscopies to characterize the intermediates generated by 77 K radiolytic cryoreduction and subsequent annealing of wild-type oxy-HO and D140A, F mutants. One-electron cryoreduction of oxy-HO yields a hydroperoxoferri-HO with g-tensor, g = [2,37, 2.187, 1.924]. Annealing of this species to 200 K is accompanied by spectroscopic changes that include the appearance of a new H-1 ENDOR signal, reflecting rearrangements in the active site. Kinetic measurements at 214 K reveal that the annealed hydroperoxoferri-HO species, denoted R, generates the ferri-alpha-meso-hydroxyheme product in a first-order reaction. Disruption of the H-bonding network within the distal pocket of HO by the alanine and phenylalanine mutations of residue D140 prevents product formation. The hydroperoxoferri-HO (D140A) instead undergoes heterolytic cleavage of the O-O bond, ultimately yielding an EPR-silent compound II-like species that does not form product. These results, which agree with earlier suggestions, establish that hydroperoxoferri-HO is indeed the reactive species, directly forming the alpha-meso-hydroxyheme product by attack of the distal OH of the hydroperoxo moiety at the heme alpha-carbon., Feb. 2002, 124, 8, 1798, 1808, Scientific journal, 10.1021/ja0122391

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, A trigonal-bipyramidal ferric aqua complex with a sterically hindered salen ligand as a model for the active site of protocatechuate 3,4-dioxygenase, H Fujii; Y Funahashi, 2002, 41, 19, 3638, 3641, Scientific journal, 10.1002/1521-3773(20021004)41:19<3638::AID-ANIE3638>3.0.CO;2-#

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• Not Refereed, 化学工業, ヘムオキシゲナーゼによる酸素活性化 金属酵素の反応場と機能の関わり, 藤井 浩, 2002, 53, 18, 24
• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, A role for highly conserved carboxylate, aspartate-140, in oxygen activation and heme degradation by heme oxygenase-1, H Fujii; XH Zhang; T Tomita; M Ikeda-Saito; T Yoshida, Heme oxygenase (HO) catalyzes the oxygen-dependent degradation of heme to biliverdinIX alpha, CO, and free iron ion via three sequential monooxygenase reactions. Although the distinct active-site structure of HO from cytochrome P450 families suggests unique distal protein machinery to activate molecular oxygen, the mechanism and the key amino acid for the oxygen activation have not been clear. To investigate the functionality of highly conserved polar amino acids in the distal helix of HO-1, we have prepared alanine mutants: T135A, R136A, D140A, and S142A, and found drastic changes in the heme degradation reactions of D140A. In this paper, we report the first evidence that D140 is involved in the oxygen activation mechanism in HO-1. The heme complexes of HO mutants examined in this study fold and bind heme normally. The pK(a) values of the iron-bound water acid autoxidation rates of the oxy-form are increased with R136A, D140A, and S142A mutations, but are not changed with T135A mutation. As the wild-type, T135A, R136A, and S142A degrade heme to verdohemeIX alpha with H2O2 and to biliverdinIXa with the NADPH reductase system. On the other hand, D140A heme complex forms compound II with H2O2, and no heme degradation occurs. For the NADPH reductase system, the oxy-form of D140A heme complex is accumulated in the reaction, and only 50% of heme is degraded. The stopped flow experiments suggest that D140A cannot activate iron-bound dioxygen and hydroperoxide properly. To investigate the carboxylate functionality of D140, we further replaced D140 with glutamic acid (D140E), phenylalanine (D140F), and asparagine (D140N). D140E degrades heme normally, but D140N shows reactivity similar to that of D140A. D140F loses heme degradation activity completely. All of these results indicate that the carboxylate at position 140 is essential to activate the iron-bound dioxygen and hydroperoxide. On the basis of the present findings, we propose an oxygen activation mechanism involving the hydrogen-bonding network through the bridging water and D140 side chain., Jul. 2001, 123, 27, 6475, 6484, Scientific journal, 10.1021/ja010490a

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Participation of carboxylate amino acid side chain in regiospecific oxidation of heme by heme oxygenase, H Zhou; CT Migita; M Sato; DY Sun; XH Zhang; M Ikeda-Saito; H Fujii; T Yoshida, Aug. 2000, 122, 34, 8311, 8312, Scientific journal, 10.1021/ja0002868

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Spin distribution in low-spin (meso-tetraalkylporphyrinato)iron(III) complexes with (d(xz),d(yz))(4)(d(xy))(1) configuration. Studies by H-1 NMR, C-13 NMR, and EPR spectroscopies, T Ikeue; Y Ohgo; T Saitoh; M Nakamura; H Fujii; M Yokoyama, H-1 NMR, C-13 NMR, and EPR studies of a series of low-spin (meso-tetraalkylporphyrinato)iron(III) complexes, [Fe(TRP)(L)(2)]X where R = Pr-n,Pr-c, and Pr-i and L represents axial ligands such as imidazoles, pyridines, and cyanide, have revealed that the ground-state electron configuration of [Fe((TPPrP)-P-n)(L)(2)]X and [Fe((TPrP)-Pr-c)(L)(2)]X is presented either as the common (d(xy))(2)(d(xz),d(yz))(3) or as the less common (d(xz),d(yz))(4)(d(xy))(1) depending on the axial ligands. The ground-state electron configuration of the isopropyl complexes [Fe(Tt-PrP)(L) (2)]X is, however, presented as (d(xz),d(yz))(4)(d(xy))(1) regardless of the kind of axial ligands. In every case, the contribution of the (d(xz),d(yz))(4)(dxy)(1) state to the electronic ground state increases in the following order: HIm < 4-Me2NPy < 2-MeIm < CN- < 3-MePy < Py < 4-CNPy. Combined analysis of the C-13 and (HNMR)-H-1 isotropic shifts together with the EPR S values have yielded the spin densities at the porphyrin carbon and nitrogen atoms. Estimated spin densities in [Fe((TPrP)-Pr-i)(4-CNPy)(2)](+), which has the purest (d(xz),d(yz))(4)(d(xy))(1) ground state among the complexes examined in this study, are as follows: meso-carbon, +0.045; alpha-pyrrole carbon, +0.0088; beta-pyrrole carbon, -0.00026; and pyrrole nitrogen, +0.057. Thus, the relatively large spin densities are on the pyrrole nitrogen and meso-carbon atoms. The result is in sharp contrast to the spin distribution in the (d(xy))(2)(d(xz,)d(yz))(3) type complexes; the largest spin density is at the beta-pyrrole carbon atoms in bis(1-methylimidazole)(meso-tetraphenylporphyrinato)iron(III), [Fe(TPP)(1-MeIm)(2)](+), as determined by Goff. The large downfield shift of the meso-carbon signal, delta +917.5 ppm at -50 degrees C in [Fe((TPrP)-Pr-i)(4-CNPy)(2)](+), is ascribed to the large spin densities at these carbon atoms. In contrast, the large upfield shift of the alpha-pyrrole carbon signal, delta -293.5 ppm at the same temperature, is caused by the spin polarization from the adjacent meso-carbon and pyrrole nitrogen atoms., May 2000, 122, 17, 4068, 4076, Scientific journal, 10.1021/ja992219n

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• Not Refereed, CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, Electron spin-echo envelope modulation spectral properties of amidate nitrogen coordinated to oxovanadium(IV) ion, K Fukui; H Fujii; H Ohya-Nishiguchi; H Kamada, Electron spin-echo envelope modulation (ESEEM) measurements have been performed for a VO2+-amidate complex, [(VO)-O-IV(hybeb)](2-) (H(4)hybeb = 1,2-bis(2-hydroxybenzamido)benzene). ESEEM spectroscopic properties of the amidate N-14 nucleus have been characterized for the first time (\ A(iso)\ = 6.70 MHz; e(2)qQ/h = 2.5 MHz, eta = 0.04) to provide a basis for the studies of vanadium-peptide interactions. The electronic structure of the amidate nitrogen is discussed., Mar. 2000, 3, 198, 199, Scientific journal, 10.1246/cl.2000.198

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Resonance raman spectra of legitimate models for the ubiquitous compound I intermediates of oxidative heme enzymes, K Czarnecki; Kincaid, JR; H Fujii, Sep. 1999, 121, 34, 7953, 7954, Scientific journal, 10.1021/ja991712w

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• Not Refereed, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, ELSEVIER SCIENCE SA, Post-assembly insertion of metal ions into thiol-derivatized porphyrin monolayers on gold, N Nishimura; M Ooi; K Shimazu; H Fujii; K Uosaki, The insertion of metal ions into thiol-derivatized free-base porphyrin monolayers pre-assembled on gold has been conducted by refluxing the metal ion solution in which the monolayer-coated gold electrode was immersed. The extent of the metal insertion was estimated from the decrease in the N1s peak in X-ray photoelectron spectra (XP spectra) assigned to the pyrrole nitrogen which binds a hydrogen atom. The insertion of Co(II) was completed by refluxing for 3 h. Although the extent of the metal insertion for the same reflux time depends on the metal ion used, the insertion of several ions including Mn(II), Fe(II), Ni(II), Cu(II) and Zn(II) was possible. Besides XP spectra, the metal insertion was confirmed by the electrocatalytic activity of the monolayers for the reduction of molecular oxygen. The structural characterization has proved that the monolayer is stable during the reflux;; neither desorption nor change in the orientation of the porphyrin molecules took place. Compared to the commonly used self-assembly of the pre-metalated porphyrins, this post-assembly metal insertion method has an advantage because neither intra nor intermolecular coordinations of the thiol functionality to the central metal ion take place, thus avoiding the unexpected disorder in the monolayer such as the formation of a multilayer, the blocking of the electrocatalytically active central metal ion and the loss of the anchoring functionality or thiol. (C) 1999 Elsevier Science S.A. All rights reserved., Sep. 1999, 473, 1-2, 75, 84, Scientific journal, 10.1016/S0022-0728(99)00287-9

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes, M Nakamura; T Ikeue; A Ikezaki; Y Ohgo; H Fujii, The electron configuration of a series of low-spin (dicyano){meso-tetrakis(2,4,6-trialkylphenyl)porphyrinato}iron(III) complexes, [Fe(R-TPP)(CN)(2)](-) where R = Me, Et, or Pr-i, together with the parent [Fe(TPP)(CN)(2)](-), has been examined in dichloromethane-methanol solution by H-1 NMR, C-13 NMR, and EPR spectroscopies. While the ferric ion of [Fe(TPP)(CN)(2)](-) has shown a common (d(xy))(2)(d(xz),d(yz))(3) configuration, the ferric ions of the alkyl-substituted complexes [Fe(R-TPP)(CN)(2)](-) have exhibited the preference of a less common (d(xz),d(yz))(4)(d(xy))(1) configuration. Spectroscopic characteristics of the complexes in which ferric ions take the (d(xz),d(yz))(4)(d(xy))(1) configuration are (i) axial type EPR spectra, (ii) downfield shifted pyrrole and meta signals in H-1 NMR spectra, and (iii) downfield shifted meso-carbon signals in C-13 NMR spectra. Occurrence of the less common (d(xz),d(yz))(4)(d(xy))(1) configuration in [Fe(R-TPP)(CN)(2)](-) has been ascribed to the electronic interaction between iron (d(pi)) and cyanide (p(pi)*) orbitals. The interaction stabilizes the d(pi) orbitals and induces (d(xz),d(yz))(4)(d(xy))(1) configuration. Since the electron configuration of (dicyano){meso-tetrakis(2,6-dichlorophenyl)porphyrinato}iron(III), [Fe(Cl-TPP)(CN)(2)](-), which carries bulky electronegative chlorine atoms at the ortho positions, is presented as a common (d(xy))(2)(d(xz),d(yz))(3), the less common (d(xz),d(yz))(4)(d(xy))(1) configuration in [Fe(R-TPP)(CN)(2)](-) can be ascribed, at least partially, to the electron-donating ability of the meso-aryl groups., Aug. 1999, 38, 17, 3857, 3862, Scientific journal, 10.1021/ic990328x

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• Not Refereed, BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY, ELSEVIER SCIENCE BV, Molecular oxygen oxidizes the porphyrin ring of the ferric alpha-hydroxyheme in heme oxygenase in the absence of reducing equivalent, CT Migita; H Fujii; KM Matera; S Takahashi; H Zhou; T Yoshida, Heme oxygenase catalyzes the regiospecific oxidative degradation of iron protoporphyrin IX (heme) to biliverdin, CO and Fe, utilizing molecular oxygen and electrons donated from the NADPH-cytochrome P-450 reductase. The catalytic conversion of heme proceeds through two known heme derivatives, alpha-hydroxyheme and verdoheme. In order to assess the requirement of reducing equivalents in the second stage of heme degradation, from alpha-hydroxyheme to verdoheme, we have prepared the alpha-hydroxyheme complex with rat heme oxygenase isoform-1 and examined its reactivity with molecular oxygen in the absence of added electrons. Upon reaction with oxygen, the majority of the alpha-hydroxyheme in heme oxygenase is altered to a species which exhibits an optical absorption spectrum with a broad Soret band, along with the minority which is converted to verdoheme. The major product species, which is electron paramagnetic resonace-silent, can be recovered to the original alpha-hydroxyheme by addition of sodium dithionite. We have also found that oxidation of the alpha-hydroxyheme-heme oxygenase complex by ferricyanide or iridium(IV) chloride yields a species which exhibits an optical absorption spectrum and reactivity similar to those of the main product of the oxygen reaction. We infer that the oxygen reaction with the ferric alpha-hydroxyheme-heme oxygenase complex forms a ferric-porphyrin cation radical. We conclude that in the absence of reducing agents, the oxygen molecule functions mainly as an oxidant for the porphyrin ring and has no role in the oxygenation of alpha-hydroxyheme. This result corroborates our previous conclusion that the catalytic conversion of alpha-hydroxyheme to verdoheme by heme oxygenase requires one reducing equivalent along with molecular oxygen. (C) 1999 Elsevier Science B.V. All rights reserved., Jul. 1999, 1432, 2, 203, 213, Scientific journal, 10.1016/S0167-4838(99)00097-7

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Insensitivity of vanadyl-oxygen bond strengths to radical type ((2)A(1u) vs (2)A(2u)) in vanadyl porphyrin cation radicals, K Czarnecki; LM Proniewicz; H Fujii; D Ji; RS Czernuszewicz; Kincaid, JR, Resonance Raman (RR) spectra are reported for vanadyl octaethylporphyrin, OV(OEP), tetramesityltetramethylporphyrin, OV(TMTMP), and tetramesitylporphyrin, OV(TMP), and their corresponding pi-cation radicals obtained by chemical and electrochemical oxidation. The behavior of the nu(2) RR porphyrin "marker band", which moves to higher frequency upon oxidation of the OV(OEP) and OV(TMTMP) and to lower frequency for OV(TMP), shows that the resultant cation radicals have predominantly (2)A(1u) and (2)A(2u) ground states, respectively. In contrast to earlier work (Macor, K. A.; Czernuszewicz, R. S.; Spiro, T. G. Inorg. Chem. 1990, 29, 1996), it is demonstrated here that the shift of the nu(V=O) is insensitive to radical type, behavior which is in agreement with similar studies of the ferryl analogues (Czarnecki, K.; et al. J. Am. Chem. Soc. 1996, 116, 2929 and 4680). It is suggested that the observed downshifts of the nu(V=O) previously reported for RR spectra of vanadyl porphyrin pi-cation radicals, relative to their neutral parents, are most reasonably ascribed to trans oxo ligand coordination (most probably a water molecule) during low-temperature electrochemical oxidation of the neutral species., Apr. 1999, 38, 7, 1543, 1547, Scientific journal, 10.1021/ic981369g

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, High-spin (meso-Tetraalkylporphyrinato)iron(III) complexes as studied by X-ray crystallography, EPR, and dynamic NMR spectroscopies, T Ikeue; Y Ohgo; A Uchida; M Nakamura; H Fujii; M Yokoyama, H-1 NMR spectra of a series of high-spin (meso-tetraalkylpsrphyrinato)iron(III) chlorides, [Fe(TRP)Cl] where R - Me, Et, Pr, or Pr-i, have been measured at various temperatures in CD2Cl2 solution. In the case of the Et,Pr, and Pr-i complexes, either the methyl or the methylene signal split into two signals with equal integral intensities at low temperature. In contrast, the Me complex did not show any splitting even at -100 degrees C. The results have been ascribed to the hindered relation of the meso-alkyl groups about C-meso-C-alpha bonds. The activation free energies for rotation have been determined as 8.0 (-72 degrees C), 8.5 (-60 degrees C), and 8.9 (-62 degrees C) kcal . mol(-1) for the Et, Pr, and Pr-i complexes, respectively, at coalescence temperatures given in parentheses. The small activation free energy for rotation of the isopropyl groups observed in the present system is explained in terms of the nonplanarity of the porphyrin ring, which has been verified both by the X-ray crystallographic analysis and by the EPR spectrum taken in a frozen CH2Cl2-toluene solution. The success in observing the hindered rotation of less bulky primary alkyl groups such as ethyl and propyl groups at an easily accessible temperature range is attributed to the large difference in chemical shifts of the mutually exchanging protons, ca. 3500 Hz in the case of the Et complex, caused by the paramagnetism of the five-coordinated ferric porphyrin complexes., Mar. 1999, 38, 6, 1276, 1281, Scientific journal, 10.1021/ic981184+

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Cobalt porphyrin heme oxygenase complex. EPR evidences for the distal heme pocket hydrogen bonding, H Fujii; Y Dou; H Zhou; T Yoshida; M Ikeda-Saito, Aug. 1998, 120, 32, 8251, 8252, Scientific journal, 10.1021/ja973925w

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Cu-63 NMR study of copper(I) carbonyl complexes with various hydrotris(pyrazolyl)borates: Correlation between Cu-63 chemical shifts and CO stretching vibrations, S Imai; K Fujisawa; T Kobayashi; N Shirasawa; H Fujii; T Yoshimura; N Kitajima; Y Moro-oka, Copper(I) carbonyl complexes with a series of hindered L-R1,L-R2 ligands (L: hydrotris(pyrazolyl)borate, R1 and R2 are substituents at the 3- and 5-positions of the pyrazole ring, respectively), (LCuCO)-Cu-R1,R2 [R1, R2 = Me, Me (1), i-Pr, i-Pr (2), t-Bu, Me (3), t-Bu, i-Pr (4), Ph, i-Pr (5), Ph, Ph (6)1 have been synthesized and characterized by]H NMR and IR spectroscopy and elemental analysis. The molecular structures of 3 and 6 have been determined by X-ray crystallography. The electronic structures of copper(I) sites are characterized by means of Cu-63 NMR spectroscopy and by the C=O stretching vibration. The sharp Cu-63 NMR signals are observed for (LCuCO)-Cu-R1,R2 complexes in toluene at room temperature. The Cu-63 NMR Signals of copper(I) complexes with alkyl-substituted ligands (1-4) are observed in lower field than those of the phenyl derivatives (5, 6) correlating with the electron-density at the copper center. This argument is supported by the good correlation between the delta((CU)-C-63) value and C=O stretching vibration which is a sensitive indicator of the extent of back-donation of the Cu d electrons to the antibonding C=O orbitals., Jun. 1998, 37, 12, 3066, 3070, Scientific journal, 10.1021/ic970138r

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Electron configuration and spin distribution in low-spin (meso-tetraalkylporphyrinato)iron(III) complexes carrying one or two orientationally fixed imidazole ligands, M Nakamura; T Ikeue; H Fujii; T Yoshimura; K Tajima, To understand the orientation effect of coordinated imidazole ligands, a series of low spin (tetraalkylporphyrinato)-iron(III) complexes, [Fe(TRP)(L)(2)](+) and [Fe(TRP)(L)(CN)], carrying at least one orientationally fixed imidazole (L) have been prepared. The H-1 NMR pyrrole signals of a series of [Fe(TRP)(2-MeIm)(2)](+) have shown considerable downfield shifts as the meso substituent becomes bulkier, from -30.4 (R = H) to +5.6 ppm (R = Pr-i) at -71 degrees C. These complexes have exhibited four pyrrole signals at lower temperature due to the hindered ligand rotation. The spread of the pyrrole signals decreases from 9.4 (Me) to 8.2 (Et) and then to 5.7 (Pr-i) ppm. The downfield pyrrole signals together with the small spread in [Fe((TPrP)-Pr-i)(2-MeIm)(2)](+) are in sharp contrast to the other low-spin complexes with orientationally fixed imidazole ligands; the chemical shifts and spreads of the pyrrole signals in [tetrakis(2,4,6-trialkylphenyl)porphyrinato]iron(III) complexes [Fe(R-TPP)(2-MeIm)(2)](+) (R = Me, Et, Pr-i) are ca. -20 and ca. 9 ppm, respectively, at -71 degrees C. The EPR spectra of a series of [Fe(TRP)(2-MeIm)(2)](+) were then taken at 4.2 K. While the R = H, Me, and Et complexes have shown so-called "large g(max) type" spectra as in the case of [Fe(R-TPP)(2-MeIm)(2)](+), the Pr-i complex has exhibited an "axial type" spectrum. The result indicates that the electron configuration of the ferric ion of [Fe((TPrP)-Pr-i)(2-MeIm)(2)](+) is presented by the unusual (d(xz), d(yz))(4)- (d(xy))(1) in contrast to the other low-spin complexes where ferric ions have the (d(xy))(2)(d(xz), d(yz))(3) configuration. When one of the 2-MeIm ligands in [Fe(TRP)(2-MeIm)(2)](+) is replaced by CN-, not only the Pr-i but also the Me and Et complexes have shown the (d(xz), d(yz))(4)(d(xy))(1) configuration as revealed from the EPR spectra. The pyrrole signals of the Pr-i complex [Fe((TPrP)-Pr-i)(2-MeIm)(CN)] have been observed at 12.2, 14.1, 14.8, and 16.2 ppm at -71 degrees C. Thus, the spread is only 4.0 ppm. The value is quite different from that of the corresponding [Fe(Me-TPP)(2-i(P)rIm)(CN)] where the spread reaches as much as 11.4 ppm. On the basis of these results, it is concluded that the spin distribution on the pyrrole beta-carbons in the complexes with (d(xz), d(yz))(4)(d(xy))(1) is rather homogeneous even if the coordinated imidazole is orientationally fixed. On the contrary, the fixation induces a larger asymmetric spin distribution on these carbons in the complexes with (d(xy))(2)(d(xz), d(yz))(3) configuration., May 1998, 37, 10, 2405, 2414, Scientific journal, 10.1021/ic9801241

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• Not Refereed, JOURNAL OF BIOLOGICAL CHEMISTRY, AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, Identification of histidine 45 as the axial heme iron ligand of heme oxygenase-2, K Ishikawa; KM Matera; H Zhou; H Fujii; M Sato; T Yoshimura; M Ikeda-Saito; T Yoshida, A truncated, soluble, and enzymatically active form of human heme oxygenase-2 (Delta HHO2) was expressed in Escherichia coli, To identify the axial heme ligand of HO-2, His-45 to Ala (Delta H45A) and His-152 to Ala (Delta H152A) mutants have been prepared using this expression system. Delta H45A could form a 1:1 complex with hemin but was completely devoid of the heme degradation activity, A 5-coordinate-type ferrous NO EPR spectrum was ob served for the heme-Delta H45A complex, The Delta H152A mutant was expressed as an inclusion body and was recovered from the lysis pellet by dissolution in urea followed by dialysis. The solubilized fraction obtained, however, was composed of a mixture of a functional enzyme and an inactive fraction. The inactive fraction was removed by Sephadex G-75 column chromatography since it eluted out of the column at the void volume, The gel filtration-purified Delta H152A exhibited spectroscopic and enzymatic properties identical to those of wild-type. We conclude, in contrast to the previous reports (McCoubrey and Maines (1993) Arch. Biochem. Biophys. 302, 402-408; McCoubrey, W, K., Jr., Huang, T, J., and Maines, M. (1997) J. Biol, Chem. 272, 12568-12574), that His 45, but not His-152, in heme oxygenase isoform-a is the proximal ligand of the heme and is essential for the heme degradation activity of the enzyme, His-152 appears to play a structural role in stabilization of the heme oxygenase protein., Feb. 1998, 273, 8, 4317, 4322, Scientific journal, 10.1074/jbc.273.8.4317

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Raman signature of the Fe2O2 "diamond" core, EC Wilkinson; YH Dong; Y Zang; H Fujii; R Fraczkiewicz; G Fraczkiewicz; RS Czernuszewicz; L Que, We report the resonance Raman (RR) spectra of iron complexes containing the Fe-2(mu-O)(2) core. Frozen CH3CN solutions of the (FeFeIV)-Fe-III intermediate [Fe-2(mu-O)(2)L-2](ClO4)(3) (where L = TPA, 5-Me-3-TPA, 5-Me-2-TPA, 5-MeTPA, 5-Et-3-TPA, or 3-Me-3-TPA) show numerous resonance-enhanced vibrations, and among these, an oxygen-isotope-sensitive vibration around 667 cm(-1) that shifts ca. 30 cm(-1) when the samples are allowed to exchange with (OH2)-O-18, and whose Raman shift does not vary with methyl substitution of the TPA ligand. Spectra of iron-isotope-substituted samples of [Fe-2(mu-O)(2)(L)2(])(ClO4)(3) (Fe-54 and Fe-57 for L = TPA, and Fe-54 and Fe-58 for L = 5-Me-3-TPA) show that this vibration is also iron-isotope sensitive. These isotopic data taken together strongly suggest that this vibration involves motion of the Fe-2(mu-O)(2) core that is isolated from motions of the Ligand. A frozen CH3CN solution of the diiron(III) complex [Fe-2(mu-O)(2)(6-Me-3-TPA)(2)](ClO4)(2) shows one intense resonance-enhanced vibration at 692 cm(-1) that shifts -30 cm(-1) with O-18 labeling. Normal coordinate analysis of the Fe-2(mu-O)(2) core in [Fe-2(mu-O)(2)(5-Me-3-TPA)(2)](ClO4)(3) supports the assignment of the Fermi doublet centered around 666.2 cm(-1) as an A(1) vibration of this core. Furthermore, we propose that this unique feature found in the region between 650 and 700 cm(-1) is indicative of a diamond core structure and is the Raman signature of an iron cluster containing this core., Feb. 1998, 120, 5, 955, 962, Scientific journal, 10.1021/ja973220u

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• Not Refereed, JOURNAL OF BIOLOGICAL CHEMISTRY, AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, The oxygen and carbon monoxide reactions of heme oxygenase, CT Migita; KM Matera; M Ikeda-Saito; JS Olson; H Fujii; T Yoshimura; H Zhou; T Yoshida, The O(2) and CO reactions with the heme, alpha-hydroxyheme, and verdoheme complexes of heme oxygenase have been studied, The heme complexes of heme oxygenase isoforms-1 and -2 have similar O(2) and CO binding properties. The O(2) affinities are very high, KO(2) = 30-80 mu M(-1), which is 30-90-fold greater than those of mammalian myoglobins, The O(2) association rate constants are similar to those for myoglobins (k(O2)', = 7-20 mu M(-1) s(-1)), whereas the O(2) dissociation rates are remarkably slow (k(O2) = 0.25 s(-1)), implying the presence of very favorable interactions between bound O(2) and protein residues in the heme pocket, The CO affinities estimated for both isoforms are only 1-6-fold higher than the corresponding O(2) affinities. Thus, heme oxygenase discriminates much more strongly against CO binding than either myoglobin or hemoglobin. The CO binding reactions with the ferrous alpha-hydroxyheme complex are similar to those of the protoheme complex, and hydroxylation at the alpha-meso position does not appear to affect the reactivity of the iron atom. In contrast, the CO affinities of the verdoheme complexes are >10,000 times weaker than those of the heme complexes because of a 100-fold slower association rate constant (k(CO)' approximate to 0.004 mu M(-1) s(-1)) and a 300-fold greater dissociation rate constant (k(CO) approximate to 3 s(-1)) compared with the corresponding rate constants of the protoheme and alpha-hydroxyheme complexes, positive charge on the verdoporphyrin ring causes a large decrease in reactivity of the iron., Jan. 1998, 273, 2, 945, 949, Scientific journal, 10.1074/jbc.273.2.945

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• Refereed, OXYGEN HOMEOSTASIS AND ITS DYNAMICS, SPRINGER-VERLAG TOKYO, Heme oxygenase: A central enzyme of oxygen-dependent heme catabolism and carbon monoxide synthesis, M Ikeda-Saito; H Fujii; KM Matera; S Takahashi; CT Migita; DL Rousseau; T Yoshida, Heme oxygenase (IIO) catalyzes the regiospecific degradation of heme to biliverdin-alpha by using O-2 and electrons donated by NADPH cytochrome P-450 reductase. The enzyme binds one equivalent of heme to form the heme-enzyme complex, and electron donation initiates the three stepwise oxygenase reactions through the two novel heme derivatives, alpha-hydroxyheme and verdoheme, during which CO and iron-biliverdin-alpha are produced; heme participates both as a prosthetic group and as a substrate. Electronic states, coordination structures, and reactivities of the HO complexes with heme, alpha-hydroxyheme, and verdoheme have been studied. The proximal iron ligand has been identified as a neutral imidazole of His-25 and the presence of a distal base has been established. Conversion to alpha-hydroxyheme is the step responsible for the regiospecificity. alpha-Hydroxyheme reveals its ferrous neutral radical state as a key property of its reactivity. Requirement of O-2 and one reducing equivalent for the conversion of ferric alpha-hydroxyheme to verdoheme has been determined. The positive charge on the macrocycle causes unique characteristics of the verdoheme complex. Combination of the novel characteristics of the catalytic intermediates and the protein environment appears to be responsible for the unique HO enzyme function., 1998, 1, 304, 314, International conference proceedings
• Refereed, OXYGEN HOMEOSTASIS AND ITS DYNAMICS, SPRINGER-VERLAG TOKYO, Heme degradation mechanism by heme oxygenase: Conversion of alpha-meso-hydroxyheme to verdoheme IX alpha, H Fujii; KM Matera; S Takahashi; CT Migita; H Zhou; T Yoshida; M Ikeda-Saito, Heme oxygenase (HO) is a microsomal enzyme that catalyzes the degradation of iron protoporphyrin IX theme) to biliverdin IXalpha through two novel heme derivatives, alpha-meso-hydroxyheme and verdoheme IXalpha. Using the recombinant HO protein and chemically synthesized alpha-hydroxyheme and verdoheme, we have elucidated HO-catalyzed heme degradation mechanisms. Heme in HO is first hydroxylated to form alpha-meso-hydroxyheme via a ferric hydroperoxide intermediate that is produced by the one-electron reduction of ferrous oxy-complex. The hydrogen bond between iron-bound dioxygen and a protein moiety may play an important role in the dioxygen reduction and regiospecific hydroxylation processes. We have shown that one electron as well as one molecular oxygen are required to degrade alpha-meso-hydroxyheme to verdoheme IXalpha and that two alternative degradation pathways are probable: ferric and ferrous. We propose here a degradation mechanism whereby the ferrous pi-neutral radical formed from ferric alpha-meso-hydroxyheme by an intramolecular electron transfer reacts with superoxide, which is produced from the reduction of dioxygen by ferric or ferrous alpha-meso-hydroxyheme to form verdoheme: IXalpha and CO. We also propose the degradation mechanism of verdoheme IXalpha to biliverdin IXalpha via dioxygen activation processes on verdoheme iron., 1998, 1, 315, 321, International conference proceedings
• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, Imidazole and p-nitrophenolate complexes of oxoiron(IV) porphyrin pi-cation radicals as models for compounds I of peroxidase and catalase, H Fujii; T Yoshimura; H Kamada, Dec. 1997, 36, 27, 6142, 6143, Scientific journal, 10.1021/ic970271j

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Change in electron configuration of ferric ion in bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)(2)](-), caused by the nonplanarity of the porphyrin ring, M Nakamura; T Ikeue; H Fujii; T Yoshimura, The synthesis and characterization of a series of bis(cyanide) (meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)(2)](-) where R is H, Me, Et, and Pr-i, are reported. The H-1 NMR spectrum of the unsubstituted [Fe(THP)(CN)(2)](-) shows a pyrrole signal at delta = -23.19 ppm (-25 degrees C) in CD2Cl2, which is quite typical as a low spin ferric complex. As the bulkiness of the meso substituent increases, the pyrrole signal moves to lower magnetic field; 0.34, -2.26, and 11.94 ppm for [Fe(TMeP)(CN)(2)](-), [Fe(TEtP)(CN)(2)](-), and [Fe((TPrP)-Pr-i)(CN)(2)](-), respectively. Corresponding to the pyrrole proton signal, the cyanide carbon signal also exhibits a large downfield shift. The difference in chemical shifts between [Fe(THP)(CN)(2)](-) and [Fe((TPrP)-Pr-i)(CN)(2)](-) reaches as much as 1443 ppm at -25 degrees C. The substituent dependent phenomena are also observed in EPR spectra taken in frozen CH2Cl2 solution at 4.2 K. While the unsubstituted complex gives a so called large g(max) type signal at 3.65, the alkyl substituted complexes exhibit axial type spectra; the EPR parameters for [Fe((TPrP)-Pr-i)(CN)(2)](-) are g(perpendicular to) = 2.43 and g(parallel to) = 1.73. These results clearly indicate that the electronic ground state changes from the usual (d(xy))(2)(d(xz), d(yz))(3) to the unusual (d(xz), d(yz))(4)(d(xy))(1) as the substituent becomes bulkier. Analysis of the EPR g values reveals that the orbital of the unpaired electron has more than 90% d(xy) character in the alkyl substituted complexes. The unusual electron configuration is ascribed to the destabilization of d(xy) orbital and/or stabilization of d(xz) and d(yz) orbitals caused by the S-4 ruffled structure of the alkyl substituted porphyrin ring. Thus, in a strongly ruffled low spin complex such as [Fe((TPrP)-Pr-i)(L)(2)](+/-), electron configuration of iron is presented by (d(xz), d(yz))(4)(d(xy))(1) regardless of the kind and basicity of the axial ligand (L). In fact, low spin bis(pyridine) complex [Fe((TPrP)-Pr-i)(Py)(2)](+) gives a pyrrole signal at quite a low field, delta = +16.4 ppm at -87 degrees C, which is actually the lowest pyrrole signal ever reported for the low spin ferric porphyrin complexes. Correspondingly, the EPR spectrum taken at 77 K showed a clear axial type spectrum, g(perpendicular to) = 2.46 and g(parallel to) = 1.59. In every case examined, (d(xz)d(yz))(4)(d(xy))(1) ground state is more or less stabilized by the addition of methanol as exemplified by the further downfield shift of the pyrrole proton and cyanide carbon signals together with the smaller EPR g(perpendicular to) values. The methanol effect is explained in terms of the stabilization of d(xz) and d(yz) relative to d(xy) due to the hydrogen bond formation between coordinated cyanide and methanol., Jul. 1997, 119, 27, 6284, 6291, Scientific journal, 10.1021/ja970602r

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, ESR studies of oxochromium(V) porphyrin complexes: Electronic structure of the Cr-V=O moiety, H Fujii; T Yoshimura; H Kamada, ESR spectra of oxochromium(V) porphyrins were obtained to investigate the electronic structure of the Cr-V=O moiety. At room temperature, the chlorooxochromium(V) meso-tetramesitylporphyrin complex 1-Cl exhibits an isotropic ESR signal, split into nine signals due to hyperfine coupling with four equivalent N-14, at g = 1.982. A small isotropic satellite signal, split into a quartet due to hyperfine coupling by the Cr-53 isotope is also observed. At 77 K, 1-Cl shows an anisotropic ESR signal with g(parallel to) = 1.986 and g(perpendicular to) = 1.980 and small satellite g(parallel to) signals arising from hyperfine coupling with the Cr-53 isotope. The ESR parameters of 1-Cl, obtained from ESR spectral simulation, show that the pi-bonding character of the Cr-V=O bond is not as strong as that of the Cr-V=N bond. To explore substituent effects on the bond character of the Cr-V=O moiety, ESR spectra of perchloratooxochromium(V) porphyrins having various electronegative substituents were recorded. With an increase in electronegativity of the meso-substituent, the gi value and the Cr-53 hyperfine coupling constant (/a(Cr-53)/) are increased. These changes suggest an increase in the ct-bonding character of the Cr-V=O moiety with an increase in the electronegativity of the meso-substituent. Furthermore, the hyperfine coupling constant of the oxo ligand, /a(O-17)/, obtained from ESR spectra of O-17-labeled oxochromium(V) porphyrin is increased with an increase in electronegativity of the meso-substituent. This indicates that the radical character of the oxo ligand is increased by the electronegative meso-substituent. These data suggest that the pi-antibonding orbital of Cr=O is destabilized with an increase in electronegativity of the meso-substituent, which may facilitate bond breaking of the Cr=O moiety in an epoxidation reaction., Mar. 1997, 36, 6, 1122, 1127, Scientific journal, 10.1021/ic960722k

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• Not Refereed, TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, Regioselective pyrrole synthesis from asymmetric beta-diketone and conversion to sterically hindered porphyrin, H Fujii; T Yoshimura; H Kamada, The condensation of asymmetric beta-diketones with alpha-oximinoacetoacetate esters affords pyrroles regioselectively. The mechanism of the regioselectivity is studied using C-13-NMR spectroscopy. Pyrrole having a neopentyl group at the 4-position is synthesized by the method, and further converted to a steric hindered porphyrin in good yield. (C) 1997 Elsevier Science Ltd., Feb. 1997, 38, 8, 1427, 1430, Scientific journal, 10.1016/S0040-4039(97)00039-7

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• Not Refereed, BIOCHEMISTRY, AMER CHEMICAL SOC, Resonance Raman spectroscopic characterization of alpha-hydroxyheme and verdoheme complexes of heme oxygenase, S Takahashi; KM Matera; H Fujii; H Zhou; K Ishikawa; T Yoshida; M IkedaSaito; DL Rousseau, Heme oxygenase (HO) is the microsomal enzyme that catalyzes the oxidative degradation of protoheme (iron protoporphyrin IX) and the generation of carbon monoxide. The enzyme converts protoheme into biliverdin through two known heme derivatives, alpha-hydroxyheme and verdoheme. To: gain insight into the degradation mechanisms of the two intermediates, the resonance Raman spectra were observed for alpha-hydroxyheme and verdoheme complexes of HO and compared with those of apomyoglobin (ape-Mb) complexes. The ferrous alpha-hydroxyheme complexed with both HO and apo-Mb shows a resonance Raman spectral pattern similar to that of the protoheme complexes. On the contrary, the ferric alpha-hydroxyheme and ferrous verdoheme complexes of HO and ape-Mb show atypical Raman patterns, which are interpreted as the result of the symmetry lowering of the porphyrin-conJugated pi-electron system. The comparison of the resonance Raman spectra of the verdoheme, complexed with HO and ape-Mb with those of the five- and six-coordinate model complexes of verdoheme shows that the ferrous forms of the verdoheme-protein complexes are six-coordinate. The Fe-CO and Fe-CN stretching frequencies of ferrous verdoheme compounds are distinct from those of ferrous heme compounds. It is inferred that the positive charge of the verdoheme ring possesses some of the charge density on the iron atom, causing unique characteristics of the iron ligand stretching vibrations and altered ligand binding properties., Feb. 1997, 36, 6, 1402, 1410, Scientific journal, 10.1021/bi962361q

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• Not Refereed, J. Inorg. Biochem, Change in electron configuration of ferric ion in bis(cyanide)(meso-tetraalkylporphyrinato)iron(III)), [Fe(TRP)(CN)2]-, caused by the nonplanarity of the porphyrin ring, M. Nakamura; T. Ikeue; H. Fujii, 1997, 67, 128, 10.1016/S0162-0134(97)80008-6

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Resonance Raman spectrum of a (2)A(1u) ferryl porphyrin pi-cation radical, K Czarnecki; LM Proniewicz; H Fujii; Kincaid, JR, Resonance Raman spectra are reported for the iron complex of tetramethyltetramesitylporphine (TMTMP) in its ferric, ferryl, and ferryl pi-cation forms. For comparison, the spectra of the copper complex and its corresponding pi-cation radical are included. Vibrational assignments have been made based on depolarization ratio measurements and isotopic frequency shifts associated with methine deuteration. The observed behavior of the v(2) and v(11) RR ''marker bands'', which shift to higher frequency upon oxidation of the macrocycle, is consistent with previously reported NMR studies wherein these radicals were shown to have predominately (2)A(1u) ground states. The v(Fe-O) stretching modes of the ferryl species (both five- and six-coordinate) and (OFeTMTMP(.+))(ClO4-) are identified by their O-16/O-18 isotope shifts. This is the first observation of the v(Fe-O) mode for a (2)A(lu), type ferryl pi-cation radical. Its frequency (833 cm(-1)) is virtually identical with that of the corresponding derivative of nzeso-tetramesitylporphyrin (TMP), (O=FeTMP(+))(ClO4-), a (2)A(2u), radical, which exhibits its v(Fe-O) mode at 835 cm(-1). These data imply that the v(Fe-O) modes of ferrylporphyrin pi-cation radicals are rather insensitive to radical type ((2)A(lu) vs (2)A(2u))-behavior which is surprisingly different from the previously observed sensitivity of the v(V-O) modes of corresponding vanadylporphyrin pi-cation radicals., May 1996, 118, 19, 4680, 4685, Scientific journal, 10.1021/ja954044x

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, ESR studies of A(1u) and A(2u) oxoiron(IV) porphyrin pi-cation radical complexes. Spin coupling between ferryl iron and A(1u)/A(2u) orbitals, H Fujii; T Yoshimura; H Kamada, This study shows the ESR spectra of oxoiron(IV) porphyrin pi-cation radicals of 1-8 in dichloromethane-methanol (5:1) mixture. We reported in a previous paper that oxoiron(IV) porphyrin pi-cation radicals of 1-4 are in an a(1u) radical state while those of 5-8 are in an a(2u) radical. The ESR spectra (g(perpendicular to)(eff) similar to 3.1 and g(parallel to)(eff) similar to 2.0) for the a(1u) radical complexes, 1-4, appear quite different from those reported previously for the oxoiron(IV) porphyrin pi-cation radical of 5 (g(y) = 4.5, g(x) = 3.6, and g(z) = 1.99). The unique ESR spectra of the a(1u) radical complexes rather resemble those of compound I from Micrococcus lysodeikticus catalase (CAT) and ascorbate peroxidase (ASP). This is the first examples to mimic the ESR spectra of compound I in the enzymes. From spectral analysis based on a spin Hamiltonian containing an exchange interaction, the ESR spectra of 1-4 can be explained as a moderate ferromagnetic state (J/D similar to 0.3) between ferryl S = 1 and the porphyrin pi-cation radical S' = 1/2. The magnitudes of zero-field splitting (D) for ferryl iron and isotropic J value, estimated from the temperature-dependence of the half-saturation power of the ESR signals, are similar to 28 and similar to+8 cm(-1)) respectively. A change in the electronegativity of the beta-pyrrole substituent hardly changes the ESR spectral feature while that of the meso-substituent slightly does owing to the change in the E/D value. On the basis of the present ESR results, we propose the a(1u) radical state for compound I of CAT and ASP., Apr. 1996, 35, 8, 2373, 2377, Scientific journal, 10.1021/ic9513752

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• Not Refereed, JOURNAL OF BIOLOGICAL CHEMISTRY, AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, Oxygen and one reducing equivalent are both required for the conversion of alpha-hydroxyhemin to verdoheme in heme oxygenase, KM Matera; S Takahashi; H Fujii; H Zhou; K Ishikawa; T Yoshimura; DL Rousseau; T Yoshida; M IkedaSaito, Heme oxygenase is a central enzyme of heme degradation and associated carbon monoxide biosynthesis. We have prepared the alpha-hydroxyheme-heme oxygenase complex, which is the first intermediate in the catalytic reaction. The active site structure of the complex was examined by optical absorption, EPR, and resonance Raman spectroscopies. In the ferric form of the enzyme complex, the heme iron is five coordinate high spin and the alpha-hydroxyheme group in the complex assumes a structure of an oxophlorin where the alpha-meso hydroxy group is deprotonated. In the ferrous form, the alpha-hydroxy group is protonated and consequently the prosthetic group assumes a porphyrin structure. The alpha-hydroxyheme group undergoes a redox-linked conversion between a keto and an enol form. The ferric alpha-hydroxyheme reacts with molecular oxygen to form a radical species. Reaction of the radical species with a reducing equivalent yields the verdoheme-heme oxygenase complex. Reaction of the ferrous alpha-hydroxyheme-heme oxygenase complex with oxygen also yields the verdoheme-enzyme complex. We conclude that the catalytic conversion of ferric alpha-hydroxyheme to verdoheme by heme oxygenase requires molecular oxygen and one reducing equivalent., Mar. 1996, 271, 12, 6618, 6624, Scientific journal, 10.1074/jbc.271.12.6618

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• Not Refereed, THIN SOLID FILMS, ELSEVIER SCIENCE SA LAUSANNE, Formation and characterization of thiol-derivatized zinc(II) porphyrin monolayers on gold, K Shimazu; M Takechi; H Fujii; M Suzuki; H Saiki; T Yoshimura; K Uosaki, Self-assembled monolayers of two kinds of thiol-derivatized porphyrins, which differ in the number of alkanethiol side chain, have been constructed on Au. X-ray photoelectron, visible and Fourier transform infrared spectra confirmed that surface structure was approximately the same as anticipated; porphyrin molecules having a single chain are somewhat tilted against surface normal, and porphyrins with four chains are oriented coplanar., Feb. 1996, 273, 1-2, 250, 253, Scientific journal, 10.1016/0040-6090(95)06790-6

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• Not Refereed, CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, Synthesis and characterization of a binuclear porphyrin complex as a model for heme a(3)-Cu-B site of cytochrome c oxidase, H Fujii; T Yoshimura; H Kamada, A binuclear complex, 1, involving copper and heme complexes is synthesized and characterized by paramagnetic H-1-NMR, FAB mass, and ESR spectroscopies. These measurements indicate a fairly weak magnetic interaction between iron and copper ions when a bridge ligand is absent., 1996, 8, 581, 582, Scientific journal, 10.1246/cl.1996.581

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, A HIGH-VALENT NONHEME IRON INTERMEDIATE - STRUCTURE AND PROPERTIES OF [FE-2(MU-O)(2)(5-ME-TPA)(2)](CLO4)(3), YH DONG; H FUJII; MP HENDRICH; RA LEISING; GF PAN; CR RANDALL; EC WILKINSON; Y ZANG; L QUE; BG FOX; K KAUFFMANN; E MUNCK, In our efforts to model the oxygen activation chemistry of methane monooxygenase (MMO) and the R2 protein of ribonucleotide reductase (RNR), we have discovered a transient green species (3) in the reaction of H2O2 with a (mu-oxo)diiron(III) TPA complex (TPA = tris(2-pyridylmethyl)amine). Our studies show that the precursor to 3 is [Fe2O(TPA)(2)(OH)(H2O)](ClO4)(3) (2a), which can be obtained by the treatment of [Fe2O(TPA)(2)(H2O)(ClO4)]-(ClO4)(3) (1) With an equivalent of base. Crystallographic studies show that 1 has a nearly linear (mu-oxo)diiron(III) core with terminal aqua and perchlorato ligands (angle Fe-(mu-O)-Fe = 174.1(4)degrees), while 2c, the 5-Et-TPA analogue of 2a, has a bent (mu-oxo)diiron(III) core that is supported by an H3O2- bridge, The presence of an H3O2- bridge in the latter is indicated by the short O-O separation (2.464(9) Angstrom), the Fe-Fe distance of 3.346(9) Angstrom, and the Fe-(mu-O)-Fe angle of 136.3(3)degrees. Thus treatment of 1 with an equivalent of base results in the replacement of the bound perchlorate with hydroxide and the bending of the Fe-O-Fe unit to form 2, That the bent Fe-O-Fe core persists in solution is indicated by its UV-vis features and NMR spectra that reflect distinct TPA coordination modes about the individual iron sites. The green intermediate 3 is generated by the reaction of 2, [Fe2O(L)(2)(OH)(H2O)](ClO4)(3) (L = TPA, 5-Me-TPA, and 5-Et-TPA), with H2O2 in CH3CN at -40 degrees C; when 5-Me-TPA is used as the tripodal ligand, 3b can be isolated as a solid upon standing overnight at -40 degrees C. Complex 3b exhibits electronic absorption features at 366 (epsilon = 7900 M(-1) cm(-1)) and 616 nm (epsilon = 5200 M(-1) cm(-1)) and an S = 3/2 EPR spectrum with g values at 4.45, 3.90, and 2.01. It exhibits one sharp Mossbauer doublet with Delta E(Q) = 0.49 mm/s and delta = 0.12 mm/s at 100 K, which accounts for 90% of the iron in the solid. Elemental analysis and electrospray ionization mass spectrometry show that 3b is a dinuclear complex best formulated as [Fe-2(O)(2)(5-Me-TPA)(2)](ClO4)(3). This dinuclear formulation is corroborated by magnetic susceptibility measurements showing that 3b has a high-temperature moment of 3.9 mu(B)/2Fe, corresponding to the 5 = 3/2 center observed by EPR. The formula for 3b suggests two unique properties: (a) that it has an Fe-2(mu-O)(2) core, and (b) that it is formally (FeFeIV)-Fe-III. The presence of an Fe-2(mu-O)(2) core in 3b is indicated by its EXAFS spectrum, which requires the inclusion of an Fe scatterer at 2.89 Angstrom for a satisfactory fit. It is further supported by the observation of resonance-enhanced Raman features at 676 and 656 cm(-1) (both of which shift to 634 cm(-1) with added (H2O)-O-18), which are associated with an Fe2O2 breathing mode by analogy to those observed for Mn2O2 complexes. The high-valent nature of 3b is corroborated by the ca. 3 eV upshift of its higher X-ray absorption K-edge relative to that of 2b and the reduction of 3b to the diiron(III) state at -40 degrees C by chemical (ferrocene titration) and cyclic voltammetric (E(1/2) = 0.96 V vs NHE) methods. Thus, 3b represents a bis(mu-oxo)-diiron complex with a formally (FeFeIV)-Fe-III valence state. Complex 3b has an unusual electronic structure. EPR, magnetization, and Mossbauer studies show that 3b has an S = 3/2 ground state with a large and nearly axial zero-field splitting, D = 35 +/- 15 cm(-1) and E/D = 0.04. The Mossbauer data show that 3 contains two equivalent iron sites which have unusually small magnetic hyperfine interactions, A = (-7.8, -7.9, -6.5) MHz. A variety of exchange coupling models are considered to describe the electronic properties of 3b; these include (FeFeIII)-Fe-III sites coupled to a ligand radical and valence-delocalized (FeFeIV)-Fe-III centers. Among the models considered, the only one that could possibly explain the observed site equivalence, isomer shift, and other properties consists of a valence-delocalized low-spin (S = 1/2) Fe-III-low-spin (S = 1) Fe-IV pair coupled by Heisenberg as well as double exchange; however, detailed theoretical studies of double exchange interactions involving low-spin iron sites are required before such an assignment can be made. Whatever its electronic structure, 3b is the only well-characterized high-valent nonheme iron species that is derived from the reaction of H2O2 and a (mu-oxo)diiron(III) complex. As such, it is relevant to the transient species observed in the oxidation chemistry of MMO and RNR R2, and provides a synthetic example of how a high-valent state can be attained in a nonheme environment., Mar. 1995, 117, 10, 2778, 2792, Scientific journal, 10.1021/ja00115a013

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, STUDIES ON THE IRON(II) MESO-OXYPORPHYRIN PI-NEUTRAL RADICAL AS A REACTION INTERMEDIATE IN HEME CATABOLISM, MORISHIMA, I; H FUJII; Y SHIRO; S SANO, The electronic structure of iron(III) meso-hydroxyporphyrin (2a) dissolved in pyridine was characterized by NMR, ESR, and optical absorption spectroscopies. It was found that the meso hydroxyl group of 2a is fully deprotonated in pyridine solution, and the resultant compound is in a quantum mixing state of the iron(III) meso-oxyporphyrin (2b) and the iron(II) porphyrin pi-neutral radical (2c) states, i.e., the resonance structure of 2b and 2c. Deprotonation of the meso hydroxyl group and coordination of the axial ligands are both essential for the generation of this unique electronic structure. The population of 2b and 2c in the mixing state is modulated by the basicity of the axial ligands. as was manifested by the drastic NMR and ESR spectral changes upon varying the pyridine derivatives as the ligands. Because 2c is highly reactive with O-2 to form verdoheme, while 2a and 2b are unreactive, the formation of the pi-radical character is essential in heme breakdown. Thus, wt discussed the electronic structure of meso-hydroxyheme in relation to the reaction of heme catabolism., Mar. 1995, 34, 6, 1528, 1535, Scientific journal, 10.1021/ic00110a035

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• Not Refereed, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH, VCH PUBLISHERS INC, CARBOXYLATOIRON(II) AGGREGATES - A NOVEL FE-4(II) COMPLEX WITH THREEFOLD SYMMETRY, S MENAGE; H FUJII; MP HENDRICH; L QUE, Sep. 1994, 33, 15-16, 1660, 1662, Scientific journal
• Not Refereed, CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, CHARACTERIZATION OF HIGH-VALENT IRON PORPHYRIN IN CATALYTIC REACTION BY IRON(III) TETRAPENTAFLUOROPHENYLPORPHYRIN, H FUJII, High valent species formed from iron(III) meso-tetra-(pentafluorophenyl)porphyrin was first prepared in dichloromethane and characterized by low-temperature UV-vis absorption spectra, proton NMR and ESR. These measurements showed the formation of oxo iron(IV) porphyrin pi-cation radical, not iron(V) porphyrin., Aug. 1994, 8, 1491, 1494, Scientific journal, 10.1246/cl.1994.1491

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, EFFECTS OF THE ELECTRON-WITHDRAWING POWER OF SUBSTITUENTS ON THE ELECTRONIC-STRUCTURE AND REACTIVITY IN OXOIRON(IV) PORPHYRIN PI-CATION RADICAL COMPLEXES, H FUJII, The effects of the electron-withdrawing power of the substituents bound to a porphyrin ring on the electronic structures and the reactivities of oxoiron(IV) porphyrin pi-cation radical complexes were studied by using 2,7,12,17-tetramethyl-3,8,13,18-tetraarylporphyrins (aryl = (1) mesityl, (2) 2-chloro-6-methylphenyl, (3) 2,6-dichlorophenyl, or (4) 2,4,6-trichlorophenyl) and tetrakis-5,10,15,20-tetraarylporphyrins (aryl = (5) mesityl, (6) 2-chloro-6-methylphenyl, (7) 2,6-dichlorophenyl, or (8) 2,4,6-trichlorophenyl). The electronic structures of oxoiron(IV) porphyrin pi-cation radicals were investigated by low-temperature UV-visible absorption spectroscopy and proton NMR measurements. The absorption spectra of oxoiron(IV) porphyrin pi-cation radicals of compounds 1-4 changed with an increase of the electron-withdrawing power of ring substituents, while those of compounds 5-8 did not. Proton NMR measurements demonstrated that oxoiron(IV) porphyrin pi-cation radicals of compounds 1-4 have an a1u radical character and that those of compounds 5-8 are better described as an a2u radical species. The reactivities of oxygen atoms of oxoiron(IV) porphyrin pi-cation radicals were examined by competitive epoxidation of cyclohexene by two oxoiron(IV) porphyrin pi-cation radicals with different radical orbital occupancies or oxidation potentials. The oxygen atom with the higher oxidation potential was more reactive than that with the lower oxidation potential. Furthermore, the oxygen atom with the a1u radical state was almost as reactive as that with the a2u radical state. The results indicate that the reactivity of the oxygen atom of the oxoiron(IV) porphyrin pi-cation radical depends on its oxidation potential and is not affected by the a1u/a2u orbital occupancy., Jun. 1993, 115, 11, 4641, 4648, Scientific journal, 10.1021/ja00064a027

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, CHARACTERIZATION AND INTRAMOLECULAR SPIN COUPLING OF A MONOMERIC A1U COPPER(II) PORPHYRIN PI-CATION RADICAL, H FUJII, The intramolecular magnetic interaction between copper(II) and a1u porphyrin radical spins in [Cu(TMTMP.)]-[SbCl6] (TMTMP. = pi-cation radical of 2,7,12,17-tetramethyl-3,8,13,18-tetramesitylporphyrin) was investigated by using ESR measurements in frozen dichloromethane and by solid magnetic susceptibility measurements. The monomeric nature of [Cu(TMTMP.)][SbCl6] at low temperature was confirmed by low-temperature UV-visible absorption spectral measurements. The radical orbital occupancy of [Cu(TMTMP.)][SbCl6] was examined by use of hyperfine-shifted deuterium NMR resonances, which showed characteristics of an a1u radical state. The ESR spectrum of [Cu(TMTMP.)][SbCl6] afforded signals having characteristics of a monomeric triplet state; i.e., the signal was separated into a four-line component from the interaction of a single copper(II) center and a pair of signals in high field. The temperature dependence of the ESR spectra of [Cu(TMTMP.)][SbCl6] signifies the S = 0 ground state (antifeffomagnetic). The solid magnetic susceptibility measurements for [Cu(TMTMP.)][SbCl6] demonstrated antiferromagnetic coupling between copper(II) and a1u radical spins with J = -120 cm-1. Antiferromagnetic coupling in [Cu(TMTMP.)][SbCl6] can be explained by the spin density at the pyrrole nitrogen atom in the a1u radical orbital., Mar. 1993, 32, 6, 875, 879, Scientific journal, 10.1021/ic00058a021

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, PREPARATION AND CHARACTERIZATION OF AN A1U OXOIRON(IV) PORPHYRIN PI-CATION-RADICAL COMPLEX, H FUJII; K ICHIKAWA, Mar. 1992, 31, 6, 1110, 1112, 10.1021/ic00032a039

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, NMR-STUDIES OF IRON(II) NITROSYL PI-CATION RADICALS OF OCTAETHYLCHLORIN AND OCTAETHYLISOBACTERIOCHLORIN AS MODELS FOR REACTION INTERMEDIATE OF NITRITE REDUCTASE, S OZAWA; H FUJII; MORISHIMA, I, Chemical oxidation of iron(II) nitrosyl complexes of octaethylchlorin (OEC) and octaethylisobacteriochlorin (OEiBC) yielded iron(II) nitrosyl pi-cation radicals. The pi-cation radicals afforded well-resolved hyperfine-shifted NMR resonances characteristic of an a2-pi-radical state. Non-Curie law behavior of the deuterium NMR resonances was interpreted in terms of a valence isomerization from the chlorin pi-cation radical to the FeIINO+ chlorin complex due to ligation of SbF6- to the iron of the pi-cation radical as well as a magnetic interaction between the NO and pi-radical spins in (OEiBC)FeIINO pi-cation radical. This valence isomerization was confirmed by variable-temperature electronic absorption spectral measurements. Furthermore, ligation of imidazole to the pi-cation radicals caused valence isomerization to yield (OEC)FeII(NO+)(Im) and (OEiBC)FeII(NO+)(Im) complexes., Feb. 1992, 114, 5, 1548, 1554, Scientific journal, 10.1021/ja00031a002

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• Not Refereed, INORGANIC CHEMISTRY, AMER CHEMICAL SOC, SPIN COUPLING IN FERRIC PORPHYRIN AND CHLORIN PI-CATION-RADICAL COMPLEXES, S NAKASHIMA; H OHYANISHIGUCHI; N HIROTA; H FUJII; MORISHIMA, I, The ferric porphyrin pi-cation-radical complexes (OEP.)Fe(III)(CIO4)2 (1) (OEP. = monoanion of octaethylporphyrin) and (OEP.)FE(III)Cl]SbCl6[ (2) and the ferric chlorin pi-cation-radical complexes (OEC.)Fe (III)(ClO4)2 (3) (OEC. = monoanion of octaethylchlorin), (OEC.)Fe (III)Cl[SbCl6] (4), and (TPC.)Fe (III)Cl[SbCl6] (5) (TPC. = monoanion of tetraphenylchlorin) were examined in microcrystalline form by magnetic susceptometry over a range of 1.6 K to room temperature at an applied field. The effective magnetic moments of the two six-coordinate complexes, 1 and 3, were in reasonable agreement with simulation in which an S = 5/2 iron ion antiferromagnetically couples with an s = 1/2 porphyrin (or chlorin) pi-radical by weak exchange interaction. In the five-coordinate complexes, 2, 4, and 5, the results of the magnetic susceptibility measurements are consistent with the calculations based on the model that the S = 5/2 iron ion antiferromagnetically couples with the s = 1/2 pi-radical with energies of -8 cm-1 for 2, -20 cm-1 for 4, and -85 cm-1 for 5. Thus the ground states of all these complexes measured are of total spin S(T) = 2. The difference in the magnitude of the antiferromagnetic coupling between the five-coordinate complexes and the six-coordinate complexes is reasonably explained by the difference of the symmetry of the radical orbitals: A1u symmetry of OEP, OEC, and TPC complexes. From these results A1u symmetry for the radical orbitals in horseradish peroxidase compound 1 (HRP compound 1) and myeloperoxidase compound I (MPO compound I) is proposed., Dec. 1990, 29, 26, 5207, 5211, Scientific journal, 10.1021/ic00351a014

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• Not Refereed, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, NMR-STUDIES OF METALLOPORPHYRIN RADICALS - IRON(II) OXOPHLORIN RADICAL FORMED FROM IRON(III) MESO-HYDROXYOCTAETHYLPORPHYRIN, MORISHIMA, I; H FUJII; Y SHIRO; S SANO, Jun. 1986, 108, 13, 3858, 3860, 10.1021/ja00273a067

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• Refereed, Inorg. Chem., Meso-Substitution Activates Oxoiron(IV) Porphyrin π-Cation Radical Complex More Than Pyrrole-ß -Substitution for Atom Transfer Reaction, Nami Fukui; Kanako Ueno; Masahiko Hada; Hiroshi Fujii, Mar. 2021, 60, 3207, 3217, Scientific journal
• Refereed, J. Inorg. Biochem., Synthesis, Characterization and Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complexes bearing Cationic N-Methyl-2-pyridinium Group, Yuna Suzuki; Masahiko Hada; Hiroshi Fujii, Jul. 2021, 111542, Scientific journal
• Refereed, Inorg. Chem., Significant Solvent Effetc on Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex: Activation in n-Alkane Solvent, Kanako Ueno; Yuri Ishimizu; Hiroshi Fujii, Jul. 2021, 60, 9243, 9247, Scientific journal
• Refereed, Inorg. Chem., Rate Limiting Step of Epoxidation Reaction of Oxoiron(IV) Porphyrin π-Cation Radical Complex: Electron Transfer Coupled Bond Formation Mechanism, Yuri Ishimizu; Zhifeng Ma; Masahiko Hada; Hiroshi Fujii, Dec. 2021, 60, 17687, 17698, Scientific journal
• Refereed, ACS Catalysis, American Chemical Society (ACS), How Do the Axial and Equatorial Ligands Modulate the Reactivity of a Metal-Bound Terminal Oxidant? An Answer from the Hypochlorite Adduct of Iron(III) Porphyrin, Sawako Yokota; Yuna Suzuki; Sachiko Yanagisawa; Takashi Ogura; Shunsuke Nozawa; Masahiko Hada; Hiroshi Fujii, 02 Sep. 2022, 12, 17, 10857, 10871, Scientific journal, 10.1021/acscatal.2c01840

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• Refereed, ACS Catalysis, American Chemical Society (ACS), Characterization and Reactivity of an Incredibly Reactive Intermediate in the Protonation Reaction of Dioxo-Manganese(V) Porphyrin with Acid, Yuri Katogi; Ayano Okamoto; Masahiko Hada; Hiroshi Fujii, 27 Mar. 2023, 4842, 4852, Scientific journal, 10.1021/acscatal.2c06122

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• Refereed, J. Ignore. Biochem., Electric Field Effect of Positive and Negative Charges of Substituents on Electronic Structure and Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, Kanae Yanai; Masahiko Hada; Hiroshi Fujii, Apr. 2023
• Refereed, ChemSusChem, Wiley, Photo‐Electro‐Biochemical H2 Production Using the Carbon Material‐Based Cathode Combined with Genetically Engineered Escherichia coli Whole‐Cell Biocatalysis, Yuki Honda; Risa Yuki; Reina Hamakawa; Hiroshi Fujii, Abio/bio hybrids, which incorporate biocatalysts that promote efficient and selective material conversions under mild conditions into existing catalytic reactions, have attracted considerable attention for developing new catalytic systems. This study constructed a H2‐forming biocathode based on a carbon material combined with whole‐cell biocatalysis of genetically‐engineered‒hydrogenase‐overproducing Escherichia coli for the photoelectrochemical water splitting for clean H2 production. Low‐cost and abundant carbon materials are generally not suitable for H2‐forming cathode due to their high overpotential for proton reduction; however, the combination of the reduction of an organic electron mediator on the carbon electrode and the H2 formation with the reduced mediator by the redox enzyme hydrogenase provides a H2‐forming cathodic reaction comparable to that of the noble metal electrode. The present study demonstrates that the recombinant E. coli whole cell can be employed as a part of the H2‐forming biocathode system, and the biocathode system wired with TiO2 photoanode can be a photoelectrochemical water‐splitting system without external voltage assistance under natural pH. The findings of this study expand the feasibility of applications of whole‐cell biocatalysis and contribute to obtaining solar‐to‐chemical conversions by abio/bio hybrid systems, especially for low‐cost, noble‐metal‐free, and clean H2 production., Oct. 2023, Scientific journal, 10.1002/cssc.202300958

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• Refereed, Catalysis Science & Technology, Royal Society of Chemistry (RSC), Tuning catalytic activity with steric and electron-withdrawing effects of a porphyrin substituent, Lulu Jiang; Yosuke Imanaka; Hiroshi Fujii, The reactivity, spectroscopic, and kinetic studies of the catalytic reactions showed that the catalytic activity is determined by the balance of the rates of the formation, reaction, and decomposition reactions of the reactive intermediate., 21 Sep. 2023, 13, 18, 5280, 5289, Scientific journal, 10.1039/d3cy00758h

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MISC

• Not Refereed, Journal of Chemical Software, Society of Computer Chemistry, Japan, High-Spin Fe(IV)-Oxo Porphyrin Complexes in Epoxidation Reaction of Olefin : A CASPT2 Study, UKAJI Kasumi; ABE Minori; HADA Masahiko; FUJII Hiroshi, High-valent iron (IV)-oxo porphyrin π-cation radical species (P+・) FeIV = O are known as an active intermediate in various enzymatic reactions of cytochrome P450s. In epoxidation reactions catalyzed by these species, potential surfaces between reactant and product are connected by the intersystem crossing. In this report, CASPT2, SO-CASPT2 and SAC-CI calculations were carried out to analyze low-lying doublet, quartet, and sextet electronic ground and excited states in an expoxidation reaction of olefin catalyzed by Cl−(P+・) FeIV = O. In both CASPT2 and SAC-CI calculations, we obtained the quartet and sextet ground states of Cl−(P+・) FeIV = O and Cl (P) FeIII respectively as suggested experimentally., 2014, 13, 3, 167, 168, 10.2477/jccj.2014-0022

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• Not Refereed, 日本放射光学会年会・放射光科学合同シンポジウム予稿集, レーザーパンプ・X線プローブ法によるRu錯体の光励起状態の構造観測, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 腰原伸也; 藤井浩; 足立伸一, 12 Jan. 2013, 26th, 96

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• Not Refereed, 物構研サイエンスフェスタ要旨集, レーザーパンプ・X線プローブ法によるRu錯体の光励起状態の構造観測, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 腰原伸也; 藤井浩; 足立伸一, 2013, 1st, 43

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• Not Refereed, PFシンポジウム要旨集, ピコ秒時間分解XAFSによる[Ru^II(bpy)₃]²⁺の³MLCT状態の観測, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 腰原伸也; 藤井浩; 足立伸一, 2012, 29th, 66

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• Not Refereed, 日本化学会講演予稿集, [Ru(bpy)₃]²⁺の100ピコ秒時間分解XAFS, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 腰原伸也; 藤井浩; 足立伸一, 12 Mar. 2010, 90th, 2, 268

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• Not Refereed, PFシンポジウム要旨集, [Ru(bpy)₃]²⁺の100ps時間分解XAFS, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 腰原伸也; 藤井浩; 足立伸一, 2010, 27th, 89

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• Not Refereed, 分子科学討論会講演プログラム&要旨(Web), [Ru(bpy)₃]²⁺の時間分解XAFS, 佐藤篤志; 野澤俊介; 富田文菜; 星野学; 星野学; 腰原伸也; 腰原伸也; 藤井浩; 足立伸一, 2010, 4th, ROMBUNNO.3B13 (WEB ONLY)

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• Not Refereed, 分子科学討論会講演プログラム&要旨(Web), ピコ秒時間分解XAFSを用いたFe(II)スピンクロスオーバー錯体における光誘起スピン転移・構造変化ダイナミクスの研究, 野澤俊介; 野澤俊介; 佐藤篤志; 佐藤篤志; 佐藤篤志; 一柳光平; 一柳光平; MATTHIEU Chollet; MATTHIEU Chollet; 富田文菜; 富田文菜; 藤井浩; 足立伸; 足立伸; 腰原伸也; 腰原伸也, 2009, 3rd, ROMBUNNO.1B14 (WEB ONLY)

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• Not Refereed, 配位化合物の光化学討論会講演要旨集, 100ピコ秒時間分解XAFSを用いた鉄(II)スピンクロスオーバー錯体における光誘起構造転移のダイナミクスの観測, 野澤俊介; 佐藤篤志; 一柳光平; MATTHIEU Chollet; 富田文菜; 市川広彦; 藤井浩; 足立伸一; 腰原伸也, 05 Aug. 2008, 21st, 58, 59

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• Not Refereed, YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN, PHARMACEUTICAL SOC JAPAN, Effect of axial ligand on compound I model complexes related to catalase and peroxidase, Akihiro Takahashi; Takuya Kurahashi; Hiroshi Fujii, 2008, 128, 48, 48, Summary international conference
• Not Refereed, JOURNAL OF INORGANIC BIOCHEMISTRY, ELSEVIER SCIENCE INC, A sterically hindered salen iron complex as a model for active sites of mononuclear non-heme iron enzymes, H Fujii; T Kurahashi; T Ogura, Jul. 2003, 96, 1, 133, 133, Summary international conference
• Not Refereed, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Formation of a pure and an admixed intermediate spin complex in saddle-shaped six-coordinated iron(III) porphyrins., M Nakamura; T Ikeue; T Yamaguchi; Y Ohgo; H Fujii, Mar. 2000, 219, U822, U822, Summary international conference
• Not Refereed, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Electron configuration of ferric ions in low spin (meso-tetraaryl porphyrinato)iron(III) complexes., M Nakamura; A Ikezaki; T Ikeue; Y Ohgo; H Fujii, Mar. 1999, 217, U1053, U1053, Summary international conference
• Not Refereed, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Homogeneous spin distribution in pyrrole beta-carbons in low spin meso-tetraalkylporphyrinatoiron(III) carrying cyanide and rotationally fixed imidazole ligands., M Nakamura; T Ikeue; Y Ohgo; H Fujii; T Yoshimura, Sep. 1997, 214, 281, INOR, Summary international conference
• Not Refereed, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, Change in electronic configuration of ferric ion in low spin porphyrin complexes caused by the nonplanarity of the porphyrin ring., M Nakamura; T Ikeue; Y Ohgo; H Fujii; T Yoshimura, Sep. 1997, 214, 413, INOR, Summary international conference
• Not Refereed, BIOPHYSICAL JOURNAL, CELL PRESS, Conversion of alpha-hydroxyhemin to verdoheme in heme oxygenase., KM Matera; S Takahashi; H Fujii; H Zhou; K Ishikawa; T Yoshimura; DL Rousseau; T Yoshida; M IkedaSaito, Feb. 1996, 70, 2, WP342, WP342, Summary international conference
• Not Refereed, RECUEIL DES TRAVAUX CHIMIQUES DES PAYS-BAS-JOURNAL OF THE ROYAL NETHERLANDS CHEMICAL SOCIETY, ELSEVIER SCIENCE BV, IRON(II)-OXOPHLORIN RADICAL, A KEY INTERMEDIATE OF THE HEME CATABOLISM, IS A RESONANCE HYBRID OF IRON(III)-MESO-OXYHEME ANION, MORISHIMA, I; H FUJII; Y SHIRO, Jun. 1987, 106, 6-7, 334, 334, Summary international conference
• ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, INT UNION CRYSTALLOGRAPHY, 100-picosecond time-resolved X-ray absorption fine structure of Fe-II(1,10-phenanthroline)(3), Tokushi Sato; Shunsuke Nozawa; Kouhei Ichiyanagi; Ayana Tomita; Hirohiko Ichikawa; Matthieu Chollet; Hiroshi Fujii; Shin-ichi Adachi; Shin-ya Koshihara, 2008, 64, C204, C205, Summary international conference, 10.1107/S0108767308093446

  DOI URL
• Solid state physics, アグネ技術センタ-, Structures and electronics states of reaction intermediates of hemoproteins, 城 宜嗣; 藤井 浩, Nov. 2008, 43, 11, 699, 710

  Permalink

Books etc

• 錯体化合物辞典, 朝倉書店, FeN4OCl, 2019
• Heme Peroxidases, Royal Society of Chemistry, 2016, Not Refereed
• クライトン「生物無機化学」, 東京化学同人, 2016, Not Refereed
• フロンティア 生物無機化学, 三共出版, 2016, Not Refereed
• 化学実験テキスト 第4版(下）, 奈良女子大学理学部化学生命環境学科化学コース, 2015, Not Refereed
• Paramagnetic Resonance of Metallobiomolecules, ACS Book Series 858, American Chemical Society, 2003, Not Refereed
• Paramagnetic Resonance of Metallobiomolecules, ACS Book Series 858, American Chemical Society, 2003, Not Refereed
• Metal-Oxo and Metal-Peroxo Species in Catalytic Oxidations, Structure & Bonding 97, Springer, 2000, Not Refereed
• Metal-Oxo and Metal-Peroxo Species in Catalytic Oxidations, Structure & Bonding 97, Springer, 2000, Not Refereed
• Oxygen Homeostasis and Its Dynamics, Springer, 1997, Not Refereed
• Oxygen Homeostasis and Its Dynamics, Springer, 1997, Not Refereed

Presentations

• 日本化学会第98回春期年会, シトクロムP450の反応活性種のモデル錯体を用いたベンジル位水酸化反応の速度論的研究, 2018
• 日本化学会第98回春期年会, 鉄4価オキソポルフィリン錯体における不均化反応の研究, 2018
• 日本化学会第97回春期年会, 鉄3価ヘム次亜塩素酸錯体のO-Cl結合開裂に対する配位子の効果, 2017
• 日本化学会第97回春期年会, 鉄4価ポルフィリンπカチオンラジカルによるオレフィンエポキシ化反応における電子移動過程への寄与について, 2017
• International Symposium on Reactive Intermediates and Unusual Molecules, Participation of Electron-Transfer process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2017
• 第11回バイオ関連化学シンポジウム, 鉄３価ヘム次亜塩素酸錯体のOCl結合開裂に対する配位子の効果, 2017
• 第67回錯体化学討論会, マンガン4価サレン錯体の配位子置換による構造 の研究, 2017
• 第67回錯体化学討論会, ヘム錯体のポルフィリン配位子及び軸配位子が 鉄の電子状態に及ぼす効果について, 2017
• 第67回錯体化学討論会, 鉄4価オキソポルフィリンπ-カチオンラジカルが触 媒するオレフィンのエポキシ化反応の電子移動過 程の寄与について, 2017
• 第50回酸化反応討論会, 疎水性反応空間を有するポルフィリン錯体の合成, 2017
• 第50回酸化反応討論会, 鉄4価オキソポルフィリンπ-カチオンラジカル錯体における配位子の構造と反応性の関係, 2017
• International Symposium on Reactive Intermediates and Unusual Molecules, Participation of Electron-Transfer process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2017
• 日本化学会第96回春期年会, マンガン４価サレン次亜塩素酸イオン付加錯体の反応性の研究, 2016
• 日本化学会第96回春期年会, 鉄(Ⅲヘム次亜塩素酸錯体の反応性に対する配位子の電子吸引性効果, 2016
• 日本化学会第96回春期年会, 鉄４価オキソ鉄ポルフィリンπカチオンラジカルと芳香環の反応および反応機構, 2016
• 日本化学会第96回春期年会, 鉄４価オキソ鉄ポルフィリンπカチオンラジカル錯体のポルフィリンラジカル軌道が反応性に及ぼす影響, 2016
• 42nd International Conference on Coordination Chemistry, The Functional Role of the Dioxo-isobacteriochlorin Structure of the Catalytic Site of Cytochrome cd1 in Nitrite Reduction, 2016
• 第66回錯体化学討論会, 鉄3価ヘム次亜塩素酸錯体の反応性に対するポルフィリン配位子と軸配位子の効果, 2016
• 第66回錯体化学討論会, Compound Iモデル錯体を用いたチトクロームP450の芳香環水酸化反応の反応機構の研究, 2016
• 第49回酸化反応討論会, 鉄4価オキソポルフィリンπ-カチオンラジカル錯体における配位子の構造と反応性の関係, 2016
• 第49回酸化反応討論会, マンガン4価サレン次亜塩素酸イオン付加錯体の同定と反応性の研究, 2016
• 8th Asian Biological Inorganic Chemistry Conference (Asbic8), Mechanism of Aromatic Hydroxylation Reactions by Compound I of Cytochrome P450, 2016
• 42nd International Conference on Coordination Chemistry, The Functional Role of the Dioxo-isobacteriochlorin Structure of the Catalytic Site of Cytochrome cd1 in Nitrite Reduction, 2016
• 8th Asian Biological Inorganic Chemistry Conference (Asbic8), Mechanism of Aromatic Hydroxylation Reactions by Compound I of Cytochrome P450, 2016
• 分子研研究会「生物無機化学の最先端と今後の展望」, ハロパーオキシダーゼの活性反応中間体の研究, 2015
• 第52回錯体化学若手の会・近畿支部勉強会, 酵素モデル金属錯体を用いた金属酵素の機能発現機構の研究, 2015
• 227th Electrochemistry Society Meeting, Role of the Heme Axial Ligand on the Reactivity of High-Valent Oxoiron(IV) Porphyrin Intermediate, 2015
• RIKEN Symposium "Metals in Biology" in Wako, Mechanism of Aromatic Hydroxylation by Cytochrome P450 Compound I Model Complexes, 2015
• IUPAC-2015, How does the Heme Axial Ligand Controles the Reactivity of High-velent oxoiron intermediates?, 2015
• ChemComm Symposium, Preparation, characterization and Reactivity of Iron(III) Porphyrin Hypochlorite Complexes as Models for Reactive Intermediates in Haloperoxidase, 2015
• 2nd Japan-Germany Joint Symposium, How does the axial ligand control the reactivity of high-valent metal oxo complex?, 2015
• 第65回錯体化学討論会, 高原子価オキソ鉄ポルフィリン錯体による芳香族水酸化反応の反応機構の研究, 2015
• 第48回酸化反応討論会, ミエロペルオキシダーゼの活性反応中間体としての鉄(Ⅲ）ヘム次亜塩素酸錯体の反応性の研究, 2015
• 第48回酸化反応討論会, Compound Iモデル錯体を用いたチトクロームP450による芳香環水酸化反応の反応機構の研究, 2015
• 第48回酸化反応討論会, マンガン4価サレン次亜塩素酸イオン付加錯体の合成と反応性の研究, 2015
• Pacifichem2015, Molecular Mechanism of Heme Axial Ligand for Controlling the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2015
• Pacifichem2015, Electronic Structure of One-electron Oxidized Mixed-Valence Metal Salen Complexes, 2015
• 227th Electrochemistry Society Meeting, Role of the Heme Axial Ligand on the Reactivity of High-Valent Oxoiron(IV) Porphyrin Intermediate, 2015
• RIKEN Symposium "Metals in Biology" in Wako, Mechanism of Aromatic Hydroxylation by Cytochrome P450 Compound I Model Complexes, 2015
• IUPAC-2015, How does the Heme Axial Ligand Controles the Reactivity of High-velent oxoiron intermediates?, 2015
• ChemComm Symposium, Preparation, characterization and Reactivity of Iron(III) Porphyrin Hypochlorite Complexes as Models for Reactive Intermediates in Haloperoxidase, 2015
• 2nd Japan-Germany Joint Symposium, How does the axial ligand control the reactivity of high-valent metal oxo complex?, 2015
• Pacifichem2015, Molecular Mechanism of Heme Axial Ligand for Controlling the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2015
• Pacifichem2015, Electronic Structure of One-electron Oxidized Mixed-Valence Metal Salen Complexes, 2015
• 8th International Conference on Porphyrins and Phthalocyanines, Functional Role of Heme Axial Ligand on the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2014
• 41st International Conference on Inorganic Chemistry, Hypochlorito-rion(III) Porphyrin Complexes as Models for Reaction Intermediates of Catalytic and Biological Reactions, 2014
• 第64回錯体化学討論会, 鉄3価ポルフィリン-次亜塩素酸イオン付加錯体の反応性に関する研究, 2014
• 第47回酸化反応討論会, 鉄3価ヘム-次亜塩素酸錯体の反応性制御機構の研究, 2014
• 8th International Conference on Porphyrins and Phthalocyanines, Functional Role of Heme Axial Ligand on the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2014
• 41st International Conference on Inorganic Chemistry, Hypochlorito-rion(III) Porphyrin Complexes as Models for Reaction Intermediates of Catalytic and Biological Reactions, 2014
• 第40回生体分子科学討論会, ハロペルオキシダーゼの活性反応中間体としての鉄３価ヘム次亜塩素酸錯体の電子構造と反応性, 2013
• 16th International Conference on Bioinorgnaic Chemsitry, Synthesis, Characterization, and Reactivity of Hypochlorite-Iron(III) Porphyrin Complexes, 2013
• 第63回錯体化学討論会, 鉄３価ヘム次亜塩素酸イオン付加錯体の合成、電子構造、反応性, 2013
• 4th Asian Conference on Coordination Chemistry, Structure and Reactivity of Iodosylarene Adduct of Manganese(IV) Salen Complex, 2013
• 第46回酸化反応討論会, 高原子価鉄オキソ錯体による酸化反応と反応性制御機構, 2013
• 16th International Conference on Bioinorgnaic Chemsitry, Synthesis, Characterization, and Reactivity of Hypochlorite-Iron(III) Porphyrin Complexes, 2013
• 4th Asian Conference on Coordination Chemistry, Structure and Reactivity of Iodosylarene Adduct of Manganese(IV) Salen Complex, 2013
• 鈴木 優菜; 本田 裕樹; 藤井 浩, 第53回酸化反応討論会, カチオン性ポルフィリン錯体の合成と反応性に関する研究, 07 Nov. 2020
• 加藤木優里; 本田裕樹; 藤井 浩, 日本化学会第100回春季年会, マンガン５価オキソポルフィリンモノ錯体の合成と反応性の研究, 23 Mar. 2020
• Yuki Honda; Yuka Shinohara; Hiroshi Fujii, 日本化学会第100回春季年会, Light-driven and mediator-free hydrogen evolution using a combination of a photosensitizer and recombinant Esherichia coli whole-cell biocatalyst, 23 Mar. 2020
• 藤井 浩; 横田 紗和子; 柳井 佳苗, 第52回酸化反応討論会, ヘム錯体による末端酸化剤の O-X 結合開裂過程の制御機構, 19 Nov. 2019
• 岡田 沙樹; 本田 裕樹; 藤井 浩, 第52回酸化反応討論会, シトクロム P450 の反応中間体モデル錯体による C-H 結合の水酸化反応の反応機構, 09 Nov. 2019
• 上野 夏奈子; 石水 友梨; 本田 裕樹; 藤井 浩, 第52回酸化反応討論会, Coumpound I モデル錯体の反応性に対する溶媒効果の研究, 09 Nov. 2019
• 竹田 彩乃; 本田 裕樹; 藤井 浩, 第52回酸化反応討論会, シトクロム P450 の活性部位のモデル錯体の反応性, 09 Nov. 2019
• Kana Nishikawa; Yuki Honda; Hiroshi Fujii, 第69回錯体化学討論会, Studies on the disproportionation reaction of iron(IV) oxo porphyrin complexes, 22 Sep. 2019
• 柳井 佳苗; 本田 裕樹; 藤井 浩, 第69回錯体化学討論会, 水溶性ヘム錯体による末端酸化剤の結合開裂過程の解 明と触媒反応の応用, 22 Sep. 2019
• 竹田 彩乃; 本田 裕樹; 藤井 浩, 第69回錯体化学討論会, シトクロムP450活性部位のモデル錯体の合成の研究, 21 Sep. 2019
• 上野 夏奈子; 石水 友梨; 本田 裕樹; 藤井 浩, 第69回錯体化学討論会, Compound-Iモデル錯体の反応性に対する溶媒効果の研究, 21 Sep. 2019
• 西川 佳那; 本田 裕樹; 藤井 浩, 第13回バイオ関連化学シンポジウム, 鉄4価オキソポルフィリン錯体の不均化反応の研究, 05 Sep. 2019
• Hiroshi Fujii, he First Asian Conference on Porphyrins, Phthalocyanines and Related Materials, What is an essential factor for determining the bond cleavage process of heme-bound terminal oxidant?, 25 Aug. 2019
• Hiroshi Fujii, International Conference on Bioinspired Small Molecule Activation, Heterolytic versus Homolytic Bond Cleavage of Hypochlorite by Iron(III) Porphyrin Complexes, 07 Jun. 2019
• 奥泉 園子; 本田 裕樹; 藤井 浩, 日本化学会第99春季年会, シトクロムP450 compound Iによる芳香族水酸化の反応選択性についての研究, 16 Mar. 2019
• Hiroshi Fujii, 9th Asian Biological Inorganic Chemistry Conference (Asbic9), Critical Factors in Determining the Reactivity of Hypochlorite Adducts of Metal Complexes, 09 Dec. 2018, 14 Dec. 2018
• 藤井 浩, 第59回錯体化学若手の会・近畿支部勉強会, ヘム錯体による次亜塩素酸の結合開裂過程の研究 酸化剤の結合開裂過程を支配するものはなにか？, 10 Nov. 2018
• 武藤 晴香; 本田 裕樹; 藤井 浩, 第51回酸化反応討論会, sMMOを模倣したN架橋二核鉄ポルフィリン錯体の合成と反応性, 01 Nov. 2018, 02 Nov. 2018
• 石水 友梨; 藤井 浩, 第51回酸化反応討論会, 鉄4価オキソポルフィリンπ-カチオンラジカルが触 媒するオレフィンのエポキシ化反応の反応機構について, 01 Nov. 2018, 02 Nov. 2018
• 岡田 沙樹; 本田 裕樹; 藤井 浩, 第51回酸化反応討論会, シトクロムP450によるアルカン水酸化反応の反応機構, 01 Nov. 2018, 02 Nov. 2018
• 奥泉 園子; 本田 裕樹; 藤井 浩, 第51回酸化反応討論会, シトクロムP450の反応活性種による芳香族化合物酸化反応の解析, 01 Nov. 2018, 02 Nov. 2018
• 岡田 沙樹; 本田 裕樹; 藤井 浩, 第12回バイオ関連化学シンポジウム, 鉄4価オキソポルフィリンπ-カチオンラジカル錯体による酸化反応の反応機構, 09 Sep. 2018, 11 Sep. 2018
• 奥泉 園子; 本田 裕樹; 藤井 浩, 第12回バイオ関連化学シンポジウム, シトクロムP450の反応活性種が触媒する芳香族水酸化反応に関する研究, 09 Sep. 2018, 11 Sep. 2018
• Hiroshi Fujii, International Symposium on Recent Advances in Bioinspired Molecular Catalysis, Marcus Theory Analysis of Aromatic Hydroxylation and Epoxidation Reactions by Compound I Model Complexes, 04 Aug. 2018, 05 Aug. 2018
• Hiroshi Fujii, 43rd International Conference on Coordination Chemistry, Heterolytic versus Homolytic Bond Cleavage of Hypochlorite by Iron Porphyrin Complexes, 31 Jul. 2018, 04 Aug. 2018
• Kana Nishikawa; Yuki Honda; Hiroshi Fujii, 43rd International Conference on Coordination Chemistry, Disproportionation of Metal(IV) Oxo Complexes, 31 Jul. 2018, 04 Aug. 2018
• 難波 照代; 小林 康浩; 瀬戸 誠; 藤井 浩, 第68回錯体化学討論会, ポルフィリン配位子が鉄3価5配位ヘムの中間スピン状態に及ぼす影響について, 28 Jul. 2018, 30 Jul. 2018
• 西川 佳那; 本田 裕樹; 藤井 浩, 第68回錯体化学討論会, 金属4価オキソ ポルフィリン錯体における不均化反応とオキソ配位子のpKaの研究, 28 Jul. 2018, 30 Jul. 2018
• Hiroshi Fujii, 10th International Conference on Porphyrins and Phthalocyanines, Participation of Electron-Transfer Process in Aromatic Hydroxylation Reactions by Heme Enzymes, 01 Jul. 2018, 06 Jul. 2018
• Hiroshi Fujii, 13th International Symposium on Activation of Dioxygen and Homogeneous Oxidation Catalysis, Participation of Electron-Transfer Processes in Oxygenation Reactions by High-valent Iron Porphyrin Complxes, 26 Jun. 2018
• Hiroshi Fujii, 2018 Korea-Taiwan-Japn Bioinorganic Chemistry Symposium, Participation of Electron-Transfer Process in Aromatic Hydroxylation Reactions by Heme Enzymes, 31 May 2018
• Hiroshi Fujii, 11th International Conference on Porphyrins and Phthalocyanines, What is an essential factor for determining the bond cleavage process of hemebound terminal oxidant?, 28 Jul. 2021
• 八束孝一; 大島奈央; 藤井 浩, 第５４回酸化反応討論会, カチオン性鉄ポルフィリン錯体を触媒とするアルカンの水酸化反応, 31 Oct. 2021
• 加藤木優里; 本田裕樹; 藤井 浩, 第５４回酸化反応討論会, マンガン 5 価モノオキソポルフィリン錯体の合成とその反応性に関する研究, 31 Oct. 2021
• Hiroshi Fujii, Pacifichem 2021, Cytochrome P450 compound I prefers hydroxylation of hydrocarbon rather than epoxidation of olefin, 20 Dec. 2021
• Hiroshi Fujii, Pacifichem 2021, Factors controlling the formation and disproportionation of high-valent oxoiron porphyrin complexes, 19 Dec. 2021
• Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, How do the porphyrin and axial ligands regulate the formation and reactivity of Compound I?, 02 Dec. 2022
• Seina Iwanoto; Ayano Takeda; Yuki Honda; Sachiko Yangisawa; Yasuhiro Kobayashi; Makoto Seto; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Metal Complex of Cytochrome P450 Active Site that can Mimic Hydrophobic Subtrate Binding Site, 29 Nov. 2022
• Nao Oshima; Yuna Suzuki; Yuki Honda; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Reactivity of Cationic Iron Porphyrin Complexes and Hydroxylation Reaction of Gaseous Alkanes, 29 Nov. 2022
• Nozomi Nakatani; Yuki Honda; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Disproportionation of Oxomanganese(IV) and Oxochromium(IV) Porphyrin Complexes, 29 Nov. 2022
• Kaho Ueda; Yuki Honda; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Mechanism of Sulfoxidation Catalyzed by Oxoiron(IV) Porphyrin π-Cation Radical Complex, 29 Nov. 2022
• 岩本 星夏; 竹田 彩乃; 本田 祐樹; 柳澤 幸子; 小林 康弘; 瀬戸 誠; 藤井 浩, 第５５回酸化反応討論会, 疎水性反応場を有するシトクロムP450活性部位モデル錯体の合成と同定, 05 Nov. 2022
• 大島 奈央; 鈴木 優菜; 本田 祐樹; 藤井 浩, 第５５回酸化反応討論会, カチオン性鉄ポルフィリン錯体を触媒としたガス状アルカンの水酸化反応, 05 Nov. 2022
• 中谷 望海; 本田 祐樹; 藤井 浩, 第５５回酸化反応討論会, マンガン４価オキソ、クロム４価オキソポルフィリン錯体の不均化反応の研究, 05 Nov. 2022
• 上田 果穂; 本田 祐樹; 藤井 浩, 第５５回酸化反応討論会, オキソ鉄４価ポルフィリンπーカチオンラジカル錯体が触媒するスルフィドの酸化反応機構の研究, 05 Nov. 2022
• 藤井 浩, 大阪大学大学院工学研究科集中講義特別セミナー, 金属酵素や金属触媒の配位環境による触媒反応の制御機構, 21 Oct. 2022
• 岩本 星夏; 竹田 彩乃; 本田 祐樹; 柳澤 幸子; 小林 康弘; 瀬戸 誠; 藤井 浩, 第７２回錯体化学討論会, 疎水性反応場を有するシトクロムP450活性部位モデル錯体の合成と同定, 25 Sep. 2022
• 大島 奈央; 鈴木 優菜; 本田 祐樹; 藤井 浩, 第７２回錯体化学討論会, カチオン性基を導入した鉄ポルフィリン錯体の反応性及びガス状アルカンの水酸化反応, 25 Sep. 2022
• Hiroshi Fujii, 8th International Conference on Coordination Chemistry, Molecular Mechanisms Controlling Formation and Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 09 Aug. 2022
• 大島 奈央; 鈴木 優菜; 本田 祐樹; 藤井 浩, 第３１回金属の関与する生体関連反応シンポジウム, カチオン性鉄ポルフィリン錯体によるガス状アルカンの水酸化反応, 18 Jun. 2022
• 岩本 星夏; 竹田 彩乃; 本田 祐樹; 柳澤 幸子; 小林 康弘; 瀬戸 誠; 藤井 浩, 第３１回金属の関与する生体関連反応シンポジウム, 疎水性環境を再現したシトクロムP450活性部位モデル錯体の合成, 18 Jun. 2022
• Hiroshi Fujii, 23rd International Conference on Cytochrome P450 (ICCP450), Molecular Mechanism Controlling Formation and Reaction Steps of Compound I, 29 Sep. 2023, 26 Sep. 2023, 29 Sep. 2023
• 森 有美; 本田 裕樹; 藤井 浩, 日本化学会第104春季年会, ルテニウム６価ジオキソポルフィリン錯体とプロトンとの反応解析, 20 Mar. 2024
• 大島 奈央; Lulu Jiang; 鈴木 優菜; 今中 庸介; 波田 雅彦; 藤井 浩, 第56回酸化反応討論会, 電子吸引性効果および電場効果によるヘム錯体触媒の活性化とガス状アルカンの水酸化反応, 11 Nov. 2023
• 上田 果穂; 本田 祐樹; 藤井 浩, 第56回酸化反応討論会, 鉄４価オキソポルフィリンπ－カチオンラジカル錯体が触媒するスルフィドの酸化反応機構の研究, 11 Nov. 2023
• Lulu Jiang; 本田 祐樹; 藤井 浩, 第56回酸化反応討論会, ヘムを用いた酸化触媒反応中では何が起こっているのか？, 11 Nov. 2023
• 足立 八重佳; 本田 祐樹; 松井 敏隆; 中澤 隆; 藤井 浩, 第56回酸化反応討論会, 好中球による生体防御の分子機構： 次亜塩素酸とヘムオキシゲナーゼの反応解析, 11 Nov. 2023
• 上田 果穂; 本田 祐樹; 藤井 浩, 第７３回錯体化学討論会, 鉄４価オキソポルフィリンπカチオンラジカル錯体が触媒するスルフィドの酸化反応機構の研究, 26 Sep. 2023
• Lulu Jiang; 本田 祐樹; 藤井 浩, 第７３回錯体化学討論会, ポルフィリン環置換基の立体及び電子吸引性効果による触媒反応の制御及びその制御機構の解明, 26 Sep. 2023
• 岡本 彩乃; 本田 祐樹; 藤井 浩, 第７３回錯体化学討論会, マンガン５価モノオキソポルフィリン錯体の合成と反応性に関する研究, 26 Sep. 2023
• 足立 八重佳; 本田 祐樹; 松井 敏隆; 中澤 隆; 藤井 浩, 第1７回バイオ関連化学シンポジウム, 次亜塩素酸のヘムオキシゲナーゼの活性中心ヘムおよび酵素タンパク質との反応の機構の解明, 08 Sep. 2023
• 山本 真帆; 篠原 優佳; 渡辺 源規; 石原 達巳; 藤井 浩; 本田 祐樹, 第７５回日本生物工学会大会, 大腸菌における金属硫化物半導体形成能の強化と光駆動水素生産への応用, 04 Sep. 2023

Research Projects

• Apr. 2022, Mar. 2025
• Apr. 2022, Mar. 2025
• Apr. 2019, Mar. 2022, Principal investigator, マンガン4価サレン錯体の配位子場による不斉構造の制御とその分子機構の解明, 藤井 浩, 科研費 新学術領域 公募研究, 0, 0, 0, Competitive research funding
• Oct. 2016, Mar. 2023, Principal investigator, 配位環境制御および反応環境制御によるメタン酸化触媒の開発, 藤井 浩, CREST, 0, 0, 0, Competitive research funding
• Apr. 2017, Mar. 2020, Principal investigator, 酸化反応に関わる金属酵素の機能発現の分子機構の研究, 藤井 浩, 科研費 基盤B, 0, 0, 0, Competitive research funding
• Reactivity and selectivity of metalloenzymes relating to biological oxidation reactions, 0, 0, 0, Competitive research funding
• Grant-in-Aid for Scientific Research (B), 01 Apr. 2017, 31 Mar. 2020, 17H03032, Study of reactions of hypochlorite with metal complexes and metalloenzymes, Fujii Hiroshi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 18590000, 14300000, 4290000, The bond cleavage processes of metal bound hypochlorite were studied to reveal the mechanism determining the bond cleavage fashion of various metal bound terminal oxidants. The reactions of heme with hypochlorite were studied with various spectroscopic methods at low temperature. The products from these reactions were also analyzed in detail. These analyses allowed us to propose a new mechanism, which can predict the bond cleavage fashion of various terminal oxidants. In addition, the mechanism controlling the reactivity of the metal bound terminal oxidants was studied with heme complexes. The reactivity of the terminal oxidants can be interpreted by the orbital interactions of the metal d-orbitals with ligand orbitals., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2004, 2006, 16350094, Control of Regioselectivity of Heme Oxygenase by Reconstruction of Hydrogen-Bonding Interactions between Substrate and Enzyme, FUJII Hiroshi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institutes of Natural Sciences, 15600000, 15600000, Regioselective reactions catalyzed by enzymes are very important biologically and chemically. Therefore, molecular mechanisms of regioselective reactions have been studied for various enzymes with various spectroscopic methods. We have studied the molecular mechanism of heme oxygenase (HO), which catalyzes regioselective degradation of heme (iron protoporphyrinIX) to α-biliverdin, CO, and free iron ion. Interestingly, HO regiospecifically oxidize the α-meso position of the heme to form α-biliverdin isomer while non-enzymatic heme degradation forms all four possible α, β, γ, δ-biliverdin isomers at nearly identical yield. We have found two essential amino acid residues, Asp-140 and Arg-183 in rat-HO, for the a-regioselective heme degradation. We showed that the Asp-140 and Arg-183 residues control oxygen activation process and the substate (heme) binding process via hydrogen-bonding interactions, respectively. With combination of the Asp-140 and Arg-183 residues, the a-meso position of the heme is placed at the nearest position from the activated oxygen species, resulting in the a-regioselective reaction. This mechanism let us imagine that we can switch the regioselectivity of HO if we can control an orientation of the heme in HO so that the other meso position is placed at the nearest position from the activated oxygen species. To realize this idea, on the basis of the crystal structure of the wild type HO, we designed a mutant, in which the other meso position is placed at the nearest position from the activated oxygen species. In this project, we succeeded in conversion of α-selective HO to δ-selective HO with the present strategy. Furthermore, we also succeeded in controlling heme orientation in HO with mutation of amino acid residues, which results in β-selective and δ-selective HO., kaken

  対象リソースIRI
• 特定領域研究, 2005, 2005, 17036071, 金属酵素のナノ反応空間における基質の配向および反応選択性の制御, 藤井 浩, 日本学術振興会, 科学研究費助成事業, 大学共同利用機関法人自然科学研究機構(共通施設), 1400000, 1400000, 酵素反応は高い立体および位置選択性を示す。これは、酵素が作る反応場の構造に由来している。酵素の反応場には基質結合サイトと活性サイトがあり、基質結合サイトは基質のある特定部位が活性サイト近傍になるように基質を固定している。そのため活性サイトから攻撃をうける部位は限定され、高い反応選択性を示すのである。我々はこの考えを逆手にとり、基質の中で我々が反応させたい部位が活性サイト近傍に位置するように酵素内で新たに基質結合サイトを再構築することができれば、ひとつの酵素からさまざまな物質を立体選択的に合成できると考えた。そこで本研究ではこの考えを検証するため、ヘムオキシゲナーゼを用いて本手法に基づいた反応選択性の人為的制御を試みた。ヘムオキシゲナーゼは、生体内で不要になったヘムタンパク質から遊離したヘムを酸化的にビリベルジンと一酸化炭素と鉄イオンに分解する酵素である。多くのヘムオキシゲナーゼはヘムのα位を酸化的に解裂させるようなα選択性をもつ。ヘムオキシゲナーゼの立体構造を基に基質結合サイトを再設計(リホーム)し、α異性体以外の我々が望む選択性をもった酵素に人工的に変換することをめざした。本年度の研究により、α選択性をもった酵素の活性中心を先に示した方針に従い再構築することにより、δ選択性をほぼ100%示す酵素に変換することに成功した。酵素の立体構造解析の結果、基質の配向が設計どおり変化していることが明らかになった。さらに、β選択性をもつ酵素に変換するための基礎的知見を得た。ヘムの配向に2つのアミノ酸残基が関わっていることを明らかにした。これにより、β選択性酵素の作成への手がかりを得ることができた。, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2002, 2003, 14340212, Synthesis and Characterization of High Valnet Reaction Intermediate of Non-Heme Iron Enzymes, FUJII Hiroshi; KURAHASHI Takuya, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Okazaki National Research Institutes, 15000000, 15000000, High-valent iron-oxo species are proposed to be the key reactive intermediate in oxidation reactions catalyzed by both heme and non-heme iron enzymes. In the case of heme enzymes, porphyrin model complexes have been extensively investigated, and oxo-iron (IV) porphyrin π-cation radical have been characterized as the most probable candidate for the active species. However, it is still unclear whether such high-valent iron-oxo species are generated from mononuclear non-heme iron active sites, in which there is no electron pool that can replace the large π-conjugation of the porphyrin ring. It is thus worth challenging to prepare transient oxidizing species from a mononuclear non-heme iron model complex for a detailed study of the electronic structure in comparison with the heme case. To this end, we have prepared a salen iron complex having a mesityl substituent, as a model for mononuclear iron enzymes. We have also tried to make a transient intermediate generated from the sterically hindered salen iron complex and m-chloroperoxybenzoic acid (mCPBA)., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research on Priority Areas, 2001, 2003, 13125208, Development of heme-based highly efficient biocatalysts, SHIMADA Hideo; FUJII Hiroshi; HAYASHI Takashi; MUKAI Kuniaki, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, KEIO UNIVERSITY, 40600000, 40600000, As a research intended to construct heme-based highly efficient biocatalyst, we have developed a functional expression system of bovine/human hybrid cytochrome oxidase in human HeLa cells by integrating the bovine mitochondrial DNA derived subunit I gene into the cell genome, whose product is the largest with 12 trans membrane helices in the 13 different enzyme-subunits and essential to the function. The expression and subsequent import of subunit I into the inner membrane of mitochondria permit the association with the other 12 human subunits leading to the hybrid enzyme having the same dioxygen reduction and proton pumping activities as those of the human enzyme, In this system, the hybrid dominates over the human enzyme. By mutating the subunit I, we have found the key residue for the proton pumping and also demonstrated that the proton pumping can be uncoupled from the dioxygen reduction. The methods we have developed ale applicable to cure mitochondrial diseases caused by mal-function of mitochondrial DNA derived membrane proteins. We have also developed the cell-free functional synthesis of Paracoccus denitrificans cytochrome oxidase by exogenously adding the prosthetic group into E. coli reaction system. The prosthetic group, protoheme, of myoglobin (Mb) can be chemically modified to functionalize the protein as monooxygenase, peroxygenase and peroxidase. Incorporation of unnatural heme, metalloporphycene, into Mb turned out to enhance the oxygen affinity to 1000-fold. Protein engineering of Mb with the above porphycene powers up the oxidizing activity enormously to allow the oxidative destruction of bisphenol A, a notable endocrine disrupter. These results revealed that unnatural heme including chemically modified are powerful to develop a protein-based efficient catalyst. Our in vivo and in vitro functional expression system of cytochrome oxidase pave the way to produce a highly efficient biocatalyst from highly hydrophobic membrane proteins by combining the protein engineering with an incorporation of unnatural heme into the active center., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 2000, 2001, 12680625, Relation between the structure and the oxygen acitivation of heme oxygenase reaction, YOSHIDA Tadashi; FUJII Hiroshi; ZHANG Xuhong, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, YAMAGATA UNIVERSITY, 3700000, 3700000, (1)The hemin complex of HmuO, a 24-kDa soluble heme degradation enzyme in Corynebacterium diphtheriae, is coordinated axially to a neutral imidazole of a proximal histidine residue in HmuO. EPR of the NO-bound ferrous heme-HmuO mutant complexes reveals His20 as the proximal heme ligand in HmuO, and this is confirmed by resonance Raman result from the ligand free ferrous heme-H20A. When bound with exogenous imidazole, His20A mutant resumes full catalytic activity. Hence, it is the absence of the proximal His ligand, that is responsible for the inactivity of proximal His mutant. (2)We found that the mutation of R183 to E or D of rat HO-1 changes the a-regioselectivity of the HO catalysis. The result shows the importance of the hydrogen bonding interaction between the arginine at position 183 and the carboxylates of the heme propionate group, as well as steric effect of the distal helix, for the a-regioselectivity. (3)Wild-type enzyme of rat HO-1 degrades heme to verdoheme with hydrogen peroxide. However, D140A heme complex forms compound II with hydrogen oeroxide, and no heme degradation occurs. D140E mutant degrades heme normally, but D140N shows reactivity similar to that of D140A. These results indicate that the carboxylate at position 140 is essential to activate the iron-bound oxygen. (4)We determined the crystal structure of rat biliverdine reductase. The structure contains two domains: an N-terminal domain characteristic of a nucleotide binding fold and a C-terminal domain. We proposed modes of binding for NADPH and biliverdin., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 2000, 2001, 12640549, Functional Alteration of Myoglobin to Nitrite Reductase by Synthetic Heme and Protein Mutations, FUJII Hiroshi; FUNAHASHI Yasuhiro, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Cente for Integrative Biosience, 3700000, 3700000, In this project, we tried to alter the function of myoglobin, which serves as an oxygen storage in a muscle, to nitrite reductase, which reduces nitrite anion to nitric oxide in denitrification process. To prepare the artificial nitrite reductase from myoglobin, we first synthesized the active site model heme of the nitrite reductase. Since heme-d_1, which has been known as an active site of the nitrite reductase, has a dioxoisobacteriochlorin core, we prepared dioxoisobacterichlorin from dimethyldeutrioporphyrin with the oxidation by osmium tetraoxide and the pinocol rearrangement. The absorption spectrum of the synthesized heme-d_1 model was similar to that of nitrite reductase, suggesting the heme-d_1 model works as an active site of the artificial nitrite reductase. Therefore, we further tried to reconstitute the heme-d_1 model into apomyoglobin. The heme-d1 model formed a stable 1 : 1 complex with the apomyoglobin. The spectroscopic data of the complex were close to those of nitrite reductase. On the basis of these results, we further tried to add the protein mutations into the complex. We prepared L29H/F45H/H64Y myoglobin mutant because the structure of the mutant seems to be close to that of nitrite reductase. The mutant myoglobin was successfully expressed by e-coli and isolated. The triple mutant was also formed stable complex with heme-d1 model complex. The artificial nitrite reductase mimics not only the spectroscopic properties but also the reactivity of nitrite reducatse., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2000, 2001, 12480176, Structure and Function of heme related proteins involved in intracellular signal transduction, IKEDA-SAITO Masao; TOMITA Takeshi; FUJII Hiroshi; SHIRO Yoshitsugu; MATSUI Toshitaka; HIROTSU Shoko, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, TOHOKU UNIVERSITY, 2200000, 2200000, In this work, we studied about heme oxygenase, a heme degradation enzyme. First, our research project was focused on constitutive isoform of mammalian heme oxygenase, HO-2. Recombinant HO-2 overexpressed in E colli. was successfully purified with new method to exclude impurity such as degradated or denatured enzymes. We used this highly purified HO-2 for crystal screening to search an appropriate buffer condition of crystallization, but we could not find the condition. On the other hand, we had already made crystal of HmuO, a bacterial heme oxygenase, and tried to elucidate crystal structure of HmuO. On the basis of spectroscopic data, optical absorption and resonance Raman spectra, and enzymological analysis of HO-2 and HmuO, their heme environment and reaction mechanism were found to be identical to those of HO-1 , inducible form of mammalian heme oxygenase. X-ray crystal structure analysis revealed that the crystal of HmuO belonged to P21 space group and a unit cell of the crystal was composed of three molecules. We could reveal structure of oxidized form and reduced form, the first and second intermediate of the enzyme reaction. The reduced form of crystal was made by the addition of sodium dithionite as an electron donor to the oxidized form crystal. Resolutions of the crystal structures were 1.4 and 1.7 angstroms for oxidized form and reduced form, respectively. From the comparison of crystal structures in oxidized and reduced forms, substantial amount of structural changes provoked by changing of heme iron electronic state were discovered for the first time. Additionally, presence of an hydrogen bonding network, which is assumed to work as a proton donor in the heme-degradation reaction, was pointed out here. Now our efforts are thrusting to realize the structure of CO adduct of HmuO as well as other intermediate, alpha-hydroxyheme form, verdoheme form, and billiverdin form., kaken

  対象リソースIRI
• 特定領域研究(A), 1999, 1999, 11116229, ^<17>O-NMRによる銅-酸素錯体の配位した酸素の電子構造と反応性の研究, 藤井 浩, 日本学術振興会, 科学研究費助成事業, 岡崎国立共同研究機構, 1500000, 1500000, 生体内には、チロシナーゼやヘモシアニンに代表されるような銅イオンを活性中心にもつ酵素が数多く存在する。ヘモシアニンは、無脊椎動物(たこやいかなど)の酸素運搬体であり、チロシナーゼはチロシンなどの酸化を行う酵素である。これら酵素の酸素付加体の構造は、ともに酸素が2つの銅イオンに対してサイドオンで配位したη_2η_2構造をもつが、ヘモシアニンに配位した酸素は可逆的に吸脱着するのに対して、チロシナーゼに配位した酸素は、活性化され基質(チロシンなど)に添加される。類似の構造をとるにもかかわらず配位した酸素の反応性が異なるのである。さらに同様な現象は、これまでの銅2核酸素錯体の反応性にも見られる。エンドオンの形態をとる場合は、配位した酸素の反応性は低く、むしろ酸素は可逆的に吸脱着するが、サイドオンの形態をとる場合は、基質を酸化することができる。 今回我々は、η_2η_2構造をもつ銅-酸素不可錯体を合成し、銅イオンに配位した酸素の^<17>O-NMR測定を行った。10%-^<17>O-エンリッチの酸素ガスから合成した酸素錯体の^<17>O-NMR測定を行った。-60度以上の温度で配位した酸素のシグナルが200ppmに観測された。温度による化学シフトの変化は観測されず、銅イオンからの常磁性の効果がないことがわかった。今回観測されたシグナルのシフトは、過酸化水素の酸素と同様の位置であり、配位した酸素がパーオキソ状態に2電子還元されていることを示した。また、配位子の違いによる化学シフトの大きな変化は観測されなかった。これらの実験から、今回観測されたシフトはη_2η_2構造をもつ酸素分子に特徴的なシフトであることが示唆された。今後さらに、配位構造が異なる錯体を合成して、その^<17>O-NMRを行い、酸素活性化を支配する因子の解明をめざす。, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (A)., 1998, 1999, 10044233, Mechanism of heme degradation by heme oxygenase, YOSHIDA Tadashi; FUJII Hiroshi; SATO Michihiko; ZHANG Xuhong; MIGITA Taiko, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, YAMAGATA UNIVERSITY, 9400000, 9400000, (1)To identify the axial heme ligand of heme oxygenase-2 (HO-2), we prepared His45 to Ala (H45A) mutant. H45A was completely devoid of the heme dedradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-H45A complex. These indicate that His 45 is the proximal ligand of heme oxygenase-2. (2)The OィイD22ィエD2 and CO reactions with the heme, hydroxyheme, and verdoheme complexes of HO were studied. The OィイD22ィエD2 affinities for heme and hydroxyheme are very high, but the CO affinities are only 1-6-fold higher than the OィイD22ィエD2 affinities. Thus, HO discriminates much more strongly against CO binding than myoglobin. (3)On the basis of Raman spectra of OィイD22ィエD2-bound form of the heme-HO complex, a highly bent Fe-O-O geometry has been proposed. However, the interaction of bound oxygen with the distal amino acid residue has not been identified. To clarify this, we have carried out EPR measurements of the cobalt(II) porphyrin HO complex and revealed that the bound-OィイD22ィエD2 formes hydrogen-bond interactions with distal amino acid residue. (4)We investigated the mechanism of the conversion of hydroxyhemin to verdoheme and confirmed that our previous conclusion that this step requires one reducing equivalent along with molecular oxygen. (5)We analyzed the first step of the heme degradation. We found that the molecular oxygen bound to heme-HO complex is stabilized by an H-bond and that hydroperoxy-HO genarated by cryoreduction catalyzes the formation of hydroxyheme. (6)We established the expression system of bacterial HO (Hmu O). Hmu O binds hemin stoichiometrically to form a hexacoordinate high spin hemin-Hmu O complex. When ascorbic acid is used as the electron donor, Hmu O converted hemin to biliverdin with hydroxyhemin and verdoheme as intermediates. Other enzymatic and protein-chemical properties closely resembled those of mammalian HOs., kaken

  対象リソースIRI
• 特定領域研究(A), 1998, 1998, 10129101, ヘムオキシゲナーゼの構造と機能との関連(特に酸素活性化について), 吉田 匡; 右田 たひ子; 藤井 浩, 日本学術振興会, 科学研究費助成事業, 山形大学, 1700000, 1700000, ヘムオキシゲナーゼ(HO)はヘムをビリベルジン,CO,鉄イオンに分解する.私共は長年本酵素によるヘム分解機構と中間過程の解析を行ってきた.最近,本酵素が病原性細菌にも存在することが知られるようになった.そこで私共は細菌のHOについても興味を持ち研究を始めた. 或る種の病原性細菌では増殖のみならずその病原性の発現の為に鉄を必要とする.即ち,これらの菌では蛋白質性毒素の遺伝子のプロモーター領域に鉄調節エレメントがあり鉄要求性に転写が促進される.一方,宿主には遊離の鉄は極微量しか存在しないためこれら細菌では鉄獲得の為に何等かの機構が必要となる.そのうちの一つに宿主を溶血させ遊離したヘモグロビンからヘムを奪い,それを菌体内に持ち込み,ヘムを分解して鉄を得る,という機構がある. 1997年にSchmittはCorynebacterium diphtheriaeに動物のHOにホモロジーを持つ25kDa蛋白質をコードする遺伝子が存在すること,そして翌年にこの蛋白質がヘム分解活性を持つ事を報告している.そこで私共もその塩基配列を化学合成し,大腸菌の発現ベクターであるpMW172に組み込み発現系と精製系を確立した.精製酵素のヘム分解比活性をアスコルビン酸-デスフェリオキサミン系で比較した所,動物系のHOよりは低いが顕著なヘム分解活性が認められた.精製酵素にヘムを加えると1対1で結合し,その光吸収像は動物系と同様にミオグロビンと類似の吸収像を示した.然し,興味深いことに吸収像はpHによって殆ど影響されなかった.従って第六配位座近傍は動物系とはかなり異なると思われる.本酵素に結合したヘムはアスコルビン酸-デスフェリオキサミン系の添加によってベルドヘムを経てビリベルジンまで分解されたので,反応過程は動物系と同じと思われる., kaken

  対象リソースIRI
• 奨励研究(A), 1997, 1998, 09740504, ヘム酵素の軸配位子が多様な酵素機能を制御する機構の解明, 藤井 浩, 日本学術振興会, 科学研究費助成事業, 2300000, 2300000, 生体内のヘム酵素は、活性中心にヘムを共通にもつが、活性中心のヘムが担う機能は多種多様である。ヘム酵素がもつ機能の多様性は、ヘムに配位する軸配位子やヘム周辺のタンパク質の作る反応場によると考えられているが、詳細は明らかでない。本研究では、生体内のベルオキシダーゼ、カタラーゼ、サトクロームP-450などのヘム酵素の軸配位子が、その酵素機能をどのように制御しているかをモデル錯体により研究した。本課題による主な成果はつぎの通りである。 1. これらのヘム酵素は、その反応中にCompound Iと呼ばれる反応中間体を生成するが、その寿命が短いため酵素を用いた詳細な研究は困難である。そこで本研究では、これら酵素と同様な軸配位子をもつCompound Iモデル錯体の合成し、軸配位子の役割りを明らかにした。軸配位子を導入するため、対イオンに過塩素酸イオンを用いること、酸化剤にオゾンを用いることにより、ベルオキシダーゼ由来のイミダゾール基とカタラーゼ由来のフェノール基をもつCompound Iモデル錯体の合成に初めて成功した。 2. 合成したCompound Iモデル錯体の吸収スペクトルを測定した。軸配位子を導入したCompound Iモデル錯体は、軸配位子をもたない錯体に比べ吸収ピークが長波長側にシフトした。この変化を軸配位子の塩基性と比較すると、塩基性が大きくなるに従い、長波長側に変化することが明らかとなった。この結果は、Compound Iの吸収ピークが酵素により大きく異なるのは、軸配位子の塩基性の違いによることを示唆した。また逆に、Compound Iの吸収位置は、軸配位子からヘム鉄への電子供与の大きさをを反映することを示した。, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 1997, 1998, 09480158, Molucular mechanisms of oxygen activation at the three steps in heme oxygenase reaction, YOSHIDA Tadashi; MIGITA Taiko; FUJII Hiroshi; ZHANG Zuhong, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, YAMAGATA UNIVERSITY, 2800000, 2800000, (1)The resonance Raman spectra for alpha-hydroxyheme and verdoheme complexes of heme oxygenase (HO) was measured. We found that the ferric alpha-hydroxyheme and ferrous verdoheme complexes showed atypical Raman patterns, which are interpreted as the result of the symmetry lowering of the porphyrin-conjugating pi-electron system. (2)To identify the axial heme ligand of HO-2, we prepared His45 to Ala (H45A) and Hisi 52 to Ala (Hi 52A) mutants. H45A was completely devoid of the heme dedradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-H45A complex, On the contrary, H152A mutant exhibited spectroscopic and enzymatic properties identical to those of wild-type. His132 of HO-1 was also not important for the heme degradation. (3)The O_2 and CO reactions with the heme, hydroxyheme, and verdoheme complexes of HO were studied. The 02 affinities for heme and hydroxyheme are very high, but the CO affinities are only 1-6-fold higher than the O_2 affinities. Thus, HO discriminates much more strongly against CO binding than myoglobin. The CO affinities of the verdoheme complexes are about 10,000 times weaker than those of the heme complex. (4)On the basis of Raman spectra of O_2-bound form of the heme-HO complex, a highly bent Fe-O-O geometry has been proposed. However, the interaction of bound oxygen with the distal amino acid residue has not been identified. To clarify this, we have carried out EPR measurements of the cobalt(II) porphyrin HO complex and revealed that the bound-O_2 forms hydrogen-bond interactions with distal amino acid residue., kaken

  対象リソースIRI
• 重点領域研究, 1997, 1997, 09235236, チトクロームC酸化酵素の活性中心モデル錯体の構築とその酸素との反応, 藤井 浩; 吉村 哲彦, 日本学術振興会, 科学研究費助成事業, (財)山形県テクノポリス財団(生物ラジカル研究所), 1700000, 1700000, チトクロームc酸化酵素は、ミトコンドリアにおいてATP合成に関わる金属酵素である。我々は、チトクロームc酸化酵素の反応機構を解明するためモデル錯体の合成を行った。 1.ヘムa_<3->Cu_B部位モデル錯体の構築 Cu_Bサイトの銅イオンには3つのヒスチジンが配位しているので、これをトリスピリジルメタンによりモデル化した。ポルフィリンとトリスピリジルメタンを化学反応性に強いエーテル結合で連結した。ポルフィリンに鉄3価イオンを、トリスピリジルメタンに銅2価イオンを導入した。合成された錯体は、吸収スペクトル、NMR、ESR、MSスペクトルの測定により、ヘム鉄と銅イオンの間に架橋配位子をもたないこと、磁気的相互作用がないことがわかった。本研究の結果、酵素のヘムa_<3->Cu_Bサイトには架橋配位子が存在することが示唆された。 2.反応中間体モデルの構築 チトクロームc酸化酵素は、CompoundI類似の反応中間体をとることがラマンスペクトルの研究により明らかにされている。CompoundI中間体の電子構造を解明するため、チトクロームc酸化酵素のCompoundI中間体のモデル化を行った。チトクロームc酸化酵素のヘムa_3は、ヒスチジン由来のイミダゾールを軸配位子としてもつ。配位力の極めて弱い過塩素酸イオンを軸配位子として用いること、また配位性のイオンを生成しないオゾンを酸化剤として用いた結果、イミダゾールを軸配位子としてもつCompoundIモデル錯体の合成に初めて成功した。合成された錯体は、鉄4価ポルフィリンπカチオンラジカル状態であること、HOMO軌道に変化がないこと、配位したイミダゾールにはほとんどラジカル電子が分布していないことが明らかとなった。, kaken

  対象リソースIRI
• 重点領域研究, 1997, 1997, 09235101, ヘムオキシゲナーゼの構造と機能との関連(特に酸素活性化について), 吉田 匡; 右田 たい子; 藤井 浩, 日本学術振興会, 科学研究費助成事業, 山形大学, 1700000, 1700000, ミクロソーム酵素であるヘムオキシゲナーゼには二つのイソ酵素がありそれぞれHO-1,HO-2と呼ばれている.ヘムは本酵素によりヒドロキシヘム,ベルドヘム,ビリベルジン・鉄錯塩を経てビリベルジン,CO,鉄イオンに酸化的に分解される.この反応に必要な電子はやはりミクロソーム酵素であるシトクロムP-450還元酵素によって供給される.ヘムだけではなくヒドロキシヘム,ベルドヘムからの反応でもそれぞれ一分子の酸素が利用される.従って,三つの連続したモノオキシゲナーゼ反応が一つの酵素蛋白の上で起こっていることになる. COはヘムの二価鉄に強い親和性を有するためCOは種々のヘム蛋白質の機能を阻害する.本反応の生成物の一つとしてCOが生ずるが,何故,このCOがヘム分解反応を阻害しないかは興味ある課題であった.そこで今年度は主にこの点について研究を行った.その結果次ぎの事実が知られた. 1.HO-1とHO-2に結合したヘム鉄の酸素やCOに対する結合能は両者とも殆ど同じであった. 2.酸素親和性はミオグロビンの場合に比べ30-90倍と極めて高かった.これは酸素結合速度はミオグロビンの場合と同じであるが,酸素解離速度が極めて遅いことによるためであった. 3.一方,CO親和性は酸素親和性とほぼ同程度であった. 4.還元型ヒドロヘキシムとの酸素及びCO親和性もヘムの場合と同様の結果であった. 5.ベルドヘムの場合はCO親和性は他のヘム蛋白質に比べ極端に低かった. 以上の実験事実と,ヘムオキゲシナーゼ反応で生じたCO濃度は反応場での酸素濃度よりも極めて低い事実とを考え合わせると,本反応で生じたCOは本反応を殆ど阻害しない理由が解明出来たことになる.一般のヘム蛋白質ではCO親和性は酸素親和性よりもかなり高いのに対し本酵素に結合したヘムの場合はそうではなかった.この点の解明は今後の大きな課題の一つである., kaken

  対象リソースIRI
• Grant-in-Aid for international Scientific Research, 1996, 1997, 08044240, Molecular mechanism of heme degradation catalyzed by heme oxygenase, YOSHIDA Tadashi; OLSON John S.; IKEDA-SAITO Masao; MIGITA Taiko; FUJII Hiroshi; ZHOU Hong, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, YAMAGATA UNIVERSITY, 11200000, 11200000, (1) We observed the resonance Raman spectra for alpha-hydroxyheme and verdoheme complexes of heme oxygensae (HO). We found that the ferric alpha-hydroxyheme and ferrous verdoheme complexes showed atypical Raman patterns, which are interpreted. as the result of the symmnetry lowering of the porphyrin-conjugating pi-electron system. (2) previously we found that histidine residue of HO was the proximal lignd of heme. To identify the axial heme lignd of HO-2, we prepared His45 to Ala (H45A) and His152 to Ala (H152A) mutants. H45A could form a 1 : 1 complex with hemin but was completely devoid of the heme degradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-H45A complex. On the contrary, H152A mutant exhibited spectroscopic and enzymatic properties identical to those of wild-type. His132 of HO-1, Which corresponds to His152 of HO-2, was also not important for the heme degradation activity. (3) The O_2 and CO reactions with the heme, alpha-hydroxyheme, and veroheme complexes of HO were studied. The heme complexs of HO-1 and HO-2 have similar O_2 and CO binding properties. The O_2 affinities for heme and hydroxyheme・are very high, but the CO affinities are only 1-6-fold higher than the O_2 affinities. Thus, HO discriminate much more strongly against CO binding than myoglobin. The CO affinities of the verdoheme complex are about 10,000 times weaker than those of the heme complex. The positive charge on the verdoporphyrin ring causes a large decrease in reactivity of the iron., kaken

  対象リソースIRI
• 基盤研究(C), 1996, 1996, 08680675, ヘムオキシゲナーゼによるヘム分解の中間過程の解析, 吉田 匡; 藤井 浩, 日本学術振興会, 科学研究費助成事業, 山形大学, 2200000, 2200000, ミクロソーム酵素であるヘムオキシゲナーゼには二つのイソ酵素があり,HO-1,HO-2と呼ばれている.両酵素ともヘムをヒドロキシヘム,ベルドヘム,ビリベルジン・鉄錯塩を経てビリベルジンに酸化的に分解する.本酵素は単純蛋白質であるが基質であるヘムを結合してできた酵素・基質複合体はヘム蛋白質の性質を持ち,その吸収像はミオグロビンのそれと酷似する.本酵素による反応ではヘムが酸素活性化のための補欠分子族としても機能している.従って,ミオグロビン型のヘムがどのように酵素を活性化できるかは興味深い.私共は先に本酵素にヘムが結合するとき,そのHis25を第五配位子(近位His)とすることを見いだした.然し,酸素の結合や活性化に関与すると思われる第六配位子については種々論議はあるものの未だ特定されていない. HO-1,HO-2の両酵素間あるいはそれぞれの酵素の動物種間で高度に保存されている部位があり,そのなかにHis132がある.従ってこのHis132が第六配位子である可能性が高いと推測されてきた.実際,1996年に米国のWilksらによってそうであると報告された.然し私共はその前年にHis132はヘム分解活性には関与していない事を既に報告しているので,再度この食い違いを検討した. その結果,やはりHis132は第六配位子ではない事を再確認し,更に両者の相違が何故生じたのかについても検討し以下の見解を得た.His132を他のアミノ酸に換えると大腸菌内で封入体として発現される.その封入体の尿素処理によって得られた再生酵素は本来の高次構造に戻ったもの(活性型)とどこかに異常のあるもの(不活性型)との混合物であったため,Wilksらが誤解したのであろう., kaken

  対象リソースIRI
• 重点領域研究, 1996, 1996, 08249101, ヘムオキシゲナーゼの構造と機能との関連(特に酸素活性化について), 吉田 匡; 藤井 浩, 日本学術振興会, 科学研究費助成事業, 山形大学, 2000000, 2000000, ヘムオキシゲナーゼ(HO)はヘムをビリベルジン,CO,鉄に酸化的に分解するミクロソーム酵素である.本酵素によるヘム分解反応では基質であるヘムが酸素活性化のための補欠分子族としても機能しているという特異な反応機構を持つ.反応機構は複雑であり,中間代謝産物としてヒドロキシヘム,ベルドヘム,ビリベルジン・鉄錯塩が存在する.この間の反応は本酵素の上で逐次的に進行し,しかもヒドロキシヘム,ベルドヘムからの反応でもそれぞれ一分子の酸素が消費されるので,三つの連続したモノオキシゲナーゼ反応が一つの酵素蛋白の上で起こっていることになる. 今回,私共はα-ヒドロキシヘムを化学合成しヘムオキシゲナーゼとの複合体を作り,それら複合体の性質や反応機構を各種生物物理学的測定法を用いて検討した.その結果次の事実が知られた. 1.酸化型α-ヒドロキシヘムはヒドロキシル基のプロトンが外れたオキソフロリン構造をとっていること.2.酸素に曝すとポルフィリン環が酸化され,構造未知の物質に転換すること.3.この物質に一電子を供給すると速やかにベルドヘムに転換すること.4.還元型ヒドロキシヘムは酸化型とは異なりオキソフロリン構造を取らないこと.5.この還元型に酸素を導入すると速やかにベルドヘムに転換すること.などが知られた.以上の結果から,ヒドロムキシヘムからベルドヘムに至る反応では一当量の還元力と酸素分子が必須であることが知られた.然し,酸素が先か電子が先かについては未だ決着がついていない. その他ベルドヘム・HO複合体も作り検討したところ,ベルドヘム・HO複合体の吸収像は私共が以前688nm物質と称した中間体のそれと同じであり,従ってベルドヘムが実際に中間体であることの最終的な結論が得られた., kaken

  対象リソースIRI
• 奨励研究(A), 1995, 1995, 07740533, ヘム酵素反応中に生成する高酸化鉄ポルフィリン錯体の反応性制御因子の解明, 藤井 浩, 日本学術振興会, 科学研究費助成事業, (財)山形県テクノポリス財団(生物ラジカル研究所), 1200000, 1200000, ペルオキシダーゼ、カタラーゼ、チトクロームP-450の活性反応中間体であるオキソ鉄4価ポルフィリンπ-カチオンラジカル錯体の電子構造をESRにより検討した。HOMO軌道の異なる2種類の錯体について検討した。a2u軌道に不対電子をもつ錯体は、g=4.4、3.6、2.0にシグナルを与えた。このスペクトルは、S=3/2のESRスペクトルであり、鉄4価イオンと不対電子が強磁性相互作用していることが明らかとなった。一方、alu軌道に不対電子をもつ錯体は、g=3.2、2.0にシグナルを与えた。このスペクトルは、錯体が特異な状態をもつことを示唆した。またこのスペクトルは酵素の中間体においても観測されており、今回酵素系の電子構造を人工的な錯体により初めて再現することができたことを示した。これは、この錯体が酵素系を研究する上で有用であることを示すものである。このスペクトルの詳細に解析した結果、先のa2u軌道の錯体と異なり、鉄4価イオンは不対電子とそれほど強く相互作用していないことがわかった。本研究の結果は、今後の酵素系の研究に重要な知見を与えるものである。 この電子構造の変化が錯体の反応性をどのように変化させるかを、速度論的手法により検討した。錯体とノルボルネンを-80℃で反応させると、エポキシドの生成が観測された。みかけの速度定数に関しては、alu、a2u錯体において大きな変化は観測されなかった。これは、HOMO軌道が反応性を制御していないことを示した。酸化電位による影響、ラジカル性と生成物の関わりは、本年度において十分に行うことができなかったので、今後検討を加え、反応性制御因子の解明をめざす。, kaken

  対象リソースIRI
• 基盤研究(B), 01 Apr. 2022, 31 Mar. 2025, 22H02096, オキソ配位子のプロトン化による金属ジオキソ錯体の活性化とC-H活性化反応の開発, 藤井 浩, 日本学術振興会, 科学研究費助成事業, 奈良女子大学, 17420000, 13400000, 4020000, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 01 Apr. 2013, 31 Mar. 2017, 25288032, Reactivity and Selectivity of Hypochlorite Adducts of Metal Complexes, Fujii Hiroshi; HADA Masahiko; OGURA Takashi; ADACHI Shinichi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, 18720000, 14400000, 4320000, In this project, we studied how hypochlorious acid is produced from the reaction of a high-valent oxoiron complex with chloride. This study points out that the key factor to produce hypochlorious acid is the reactivity of the high-valent oxoiron intermediate that is controlled by unique coordination structures of the active sites in the enzymes. In addition, we studied how the reactivity of the hypochlorite adduct complex is controlled. The most important factor to control the reactivity of the complex is electron donor ability form the cis- and trans-ligands. Interestingly, the electron donor effect of these two ligands show different trend to the reactivity., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2010, 2012, 22350030, Molecular Mechanism Controlling Reactivity and Selectivity of High-Valent Oxo-Metal Complexes, FUJII Hiroshi; KURAHASHI Takuya; HADA Masahiko, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, National Institutes of Natural Sciences Okazaki Research Facilities, 19370000, 14900000, 4470000, In this project, we studied how the reactivity and selectivity of high-valent metal-oxo complexes are controlled to provide a new concept fordeveloping functional catalysts.We succeeded in revealing a new unique molecular mechanisms that the axial ligand controls the reactivity of oxoiron(IV) porphyrin π-cation radical complex by stability of the iron(III) porphyrin complex, not by instability of itself. In addition, we succeeded in solving the crystal structure of a chiral manganese(IV) salen iodosylarene adduct, which provide a new mechanism for controlling its enantioselectivity, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2010, 2012, 22350010, Quantum-Chemical Study on Magnetic Molecular Properties andChemical Reactions in Excited States Based on the RelativisticSAC-CI Theory, HADA Masahiko; HASEGAWA Junya; FUJII Hiroshi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Tokyo Metropolitan University, 16770000, 12900000, 3870000, The main purpose of this project is to make a new theoretical and computational development of the higher-order relativistic GUHF-CCSD-CI method for chemical reactions and chemical phenomena in the electronic excited states, for example, photochemical reactions and fine potential energy surface considering the spin-orbit interaction and the intersystem crossing. In the GUHF-CCSD-CI method, the GUHF orbitals are used as reference and the CCSD is used for the electronic ground state. We finished the computer code of the GUHF-CCSD-CI method, and we applied this code to calculations of the singlet and triplet excited states and checked the accuracy in comparison with the non-relativistic CCSD, SO-CASPT2. The GUHF-CCSD-CI is meaningfully more accurate than the other methods. The SO-CASPT2 is accurate in light elements but not in heavy elements. Further, we carried out some relativistic quantum-chemical calculations for compounds containing heavy-elements., kaken

  対象リソースIRI

Ⅲ．社会連携活動実績

１．公的団体の委員等（審議会、国家試験委員、他大学評価委員，科研費審査委員等）

• Apr. 2017, 9999, Society
• Oct. 2022, 9999, Society