藤井　浩Fujii Hiroshiフジイ　ヒロシ

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プロフィール情報

• 姓

  藤井, フジイ

• 名

  浩, ヒロシ

学位

• 工学博士, 京都大学

研究キーワード

• 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

研究分野

• ナノテク・材料, 無機・錯体化学
• ライフサイエンス, 機能生物化学

経歴

• 2014年04月, 9999年, 奈良女子大学, 研究院 自然科学系 化学領域, 教授
• 2014年04月, 9999年, :Professor, Graduate School of Humanities and Sciences and Department of Chemistry, Biology, and Environment Sciences, Nara Women's University
• 2007年04月, 2014年03月, :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年, 2014年, :Associate Professor, Okazaki Institute of Integrative Bioscience, National Institutes of Natural Sciences
• 2004年04月, 2007年03月, :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年, 2007年, :Associate Professor, Okazaki Institute of Integrative Bioscience, National Institutes of Natural Sciences
• 2001年02月, 2004年03月, :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年, 2004年, :Associate Professor, Center for Integrative Bioscience, Okazaki National Research Institutes
• 1998年03月, 2001年01月, :岡崎国立共同研究機構分子科学研究所 助教授
• 1998年, 2001年, :Associate Professor, Institute for Molecular Science, Okazaki National Research Institutes
• 1994年02月, 1998年02月, :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年, 1998年, :Chief Scientist, Yamagata Technopolis Foundation, Institute for Life Support Technology
• 1992年11月, 1994年01月, :ミネソタ大学化学科 博士研究員
• 1992年, 1994年, Post-doctoral Fellow, University of Minnesota
• 1990年04月, 1992年10月, :北海道大学理学部化学科 助手
• 1990年, 1992年, :Assistant Professor, Department of Chemistry, Faculty of Science, Hokkaido University

学歴

• 1987年04月, 1990年03月, 京都大学大学院, 工学研究科, 分子工学専攻博士後期課程, 日本国
• 1985年04月, 1987年03月, 京都大学大学院, 工学研究科, 分子工学専攻修士課程
• 1981年04月, 1985年03月, 金沢大学, 工学部, 工業化学科

所属学協会

• 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

論文

• 査読あり, 英語, J. Inorg. Biochem., Resonance Raman Study of Oxoiron(IV) Porphyrin π-Cation Radical Complex: Porphyrin Ligand Effect on ν(Fe=O) Frequency, in press
• 査読あり, 英語, ChemBioChem., 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., 2020年12月, 21, 23, 3389, 3397, 研究論文（学術雑誌）, 10.1002/cbic.202000383

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• 査読あり, その他, Catalysis Science & Technology, 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.

  , 2020年09月, 10, 17, 6006, 6012, 研究論文（学術雑誌）, 10.1039/d0cy01099e

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• 査読あり, その他, 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, 2020年07月, 22, 12173, 12179
• 査読あり, その他, 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, 2020年03月, 142, 4980, 4984
• 査読あり, 英語, Bull. Chem Soc. Jpn., 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., 2020年02月, 93, 2, 187, 193, 研究論文（学術雑誌）, 10.1246/bcsj.20190293

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• 査読あり, その他, Biochemistry, 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年, 59, 40, 3918, 3928, 研究論文（学術雑誌）, 10.1021/acs.biochem.0c00731

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• 査読あり, その他, Comprehesive Coordination Chemsitry III, Dioxygen-Binding in Metalloproteins and Corresponding Models, Shinobu Itoh; Hiroshi Fujii, 2021年, 8, 200, 237, 研究論文（学術雑誌）, 10.1016/b978-0-12-409547-2.14904-2

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• 査読あり, 英語, 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., 2019年03月01日, 25, 13, 3369, 3375, 研究論文（学術雑誌）, 10.1002/chem.201805580

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• 査読あり, 英語, 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年, 58, 8263, 8266, 研究論文（学術雑誌）
• 査読あり, 英語, 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年, 58, 10863, 10866, 研究論文（学術雑誌）
• 査読あり, 英語, 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年, 24, 483, 494, 研究論文（学術雑誌）
• 査読あり, 英語, 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年, 40, 19, 1780, 1788, 研究論文（学術雑誌）, 国際誌, 10.1002/jcc.25831

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• 査読あり, 英語, Journal of the 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., 2018年04月18日, 140, 15, 5127, 5137, 研究論文（学術雑誌）, 10.1021/jacs.7b13037

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• 査読無し, 英語, Inorganic Chemistry, 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., 2018年02月19日, 57, 4, 1685, 1688, 研究論文（学術雑誌）, 10.1021/acs.inorgchem.7b02661

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• 査読あり, 英語, 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年, 19, 2156, 2159, 研究論文（学術雑誌）
• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2016年07月, 138, 26, 8048, 8051, 研究論文（学術雑誌）, 10.1021/jacs.6b03223

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• 査読無し, 英語, Bull. Chem. Soc. Jp., The Origin of Relative Stability of Di-μ-oxo M-M Chiral Salen Complexes [M-M = Ti (IV)-Ti(IV), V(IV)-V(IV), Cr(IV)-Cr(IV) and Mn(IV)-Mn(IV)]: A Quantum-Chemical Analysis, Fujii Hiroshi; Radhika Narayanan; Archana Velloth; Takuya Kurahashi; 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., 2016年04月, 89, 4, 447, 454, 研究論文（学術雑誌）, 10.1246/bcsj.20150393

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• 査読無し, 英語, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 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., 2016年04月, 113, 14, 3779, 3784, 研究論文（学術雑誌）, 10.1073/pnas.1523333113

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• 査読無し, 英語, CHEMICAL SCIENCE, 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年, 7, 4, 2896, 2906, 研究論文（学術雑誌）, 10.1039/c5sc04825g

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• 査読無し, 英語, Inorg. Chem., Factors Affecting Hydrogen-Tunneling Contribution in Hydroxylation Reactions Promoted by Oxoiron(IV) Porphyrin π-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., 2014年10月, 53, 19, 10632, 10641, 研究論文（学術雑誌）, 10.1021/ic501737j

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• 査読無し, 英語, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 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., 2014年03月, 10, 3, 1062, 1073, 研究論文（学術雑誌）, 10.1021/ct401014p

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• 査読無し, 英語, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, Synthesis, Characterization, and Reactivity of Hypochlorito-Iron(III) Porphyrin Complexes, H. Fujii; Z. Cong; T. Kurahashi; S. Yanagisawa; T. Ogura, 2014年03月, 19, S159, S159
• 査読無し, 英語, Inorg. Chem., Di-µ-Oxo Dimetal Core of MnIV and TiIV as a Linker Between Two Chiral Salen Complexes Leading to the Stereoselective Formation of Different M- and P-Helical Structure, 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., 2014年01月, 53, 2, 1070, 1079, 研究論文（学術雑誌）, 10.1021/ic402572h

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2013年08月, 52, 16, 9557, 9566, 研究論文（学術雑誌）, 10.1021/ic401270j

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2013年04月, 52, 7, 3908, 3919, 研究論文（学術雑誌）, 10.1021/ic302677f

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• 査読無し, その他, 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年, 62
• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2012年12月, 134, 51, 20617, 20620, 研究論文（学術雑誌）, 10.1021/ja3108774

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• 査読無し, 英語, BULLETIN OF THE CHEMICAL SOCIETY OF 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., 2012年09月, 85, 9, 940, 947, 研究論文（学術雑誌）, 10.1246/bcsj.20120146

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• 査読無し, 英語, Inorg. Chem., Effect of the Axial Ligand on the Reactivity of the Oxoiron(IV) Porphyrin π-Cation Radical Complex: Higher Stabilization of the Product State Relative to the Reactant State, 藤井 浩; 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., 2012年07月, 51, 13, 7296, 7305, 研究論文（学術雑誌）, 10.1021/ic3006597

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• 査読無し, 英語, J. Phys. Chem. C, 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, 藤井 浩; Tokushi Sato; Shunsuke Nozawa; Ayana Tomita; Manabu Hoshino; Shin-ya Koshihara; Hiroshi Fujii; Sin-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)., 2012年07月, 116, 27, 14232, 14236, 研究論文（学術雑誌）, 10.1021/jp3038285

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• 査読無し, 英語, J. Am. Chem. Soc., Formation of Iron(III) meso-Chloro-isoporphyrin as a Reactive Chlorinating Agent from Oxoiron(IV) Porphyrin π-Cation Radical, 藤井 浩; 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., 2012年03月, 134, 10, 4469, 4472, 研究論文（学術雑誌）, 10.1021/ja209985v

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• 査読無し, 英語, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Structure and Reactivity of an Iodosylarene Adduct of a Manganese(IV)-Salen Complex, Chunlan Wang; Takuya Kurahashi; Hiroshi Fujii, 2012年, 51, 31, 7809, 7811, 研究論文（学術雑誌）, 10.1002/anie.201202835

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• 査読無し, 英語, CHEMICAL SCIENCE, 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年, 3, 2, 391, 397, 研究論文（学術雑誌）, 10.1039/c1sc00725d

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• 査読無し, 英語, Inorg. Chem., Redox Potentials of Oxoiron(IV) Porphyrin π-Cation Radical Complexes: Participation of Electron Transfer Process in Oxygenation Reactions, 藤井 浩; 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., 2011年08月, 50, 15, 6922, 6928, 研究論文（学術雑誌）, 10.1021/ic102564e

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2011年06月, 133, 21, 8307, 8316, 研究論文（学術雑誌）, 10.1021/ja2016813

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• 査読無し, 英語, Angew. Chemie. Int. Ed., Oxidation of Chloride and Subsequent Chlorination of Organic Compounds by Oxoiron(IV) Porphyrin π-Cation Radicals, 藤井 浩; Zhiqi Cong; Takuya Kurahashi; Hiroshi Fujii, 2011年, 50, 42, 9935, 9939, 研究論文（学術雑誌）, 10.1002/anie.201104461

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• 査読無し, 日本語, 錯体化学会誌, Japan Society of Coordination Chemistry, 高酸化サレン錯体を鍵とする不斉酸化触媒や金属酵素の機能発現機構の研究, 藤井 浩; 倉橋 拓也, 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年, 57, 57, 66, 10.4019/bjscc.57.57

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2010年07月, 49, 14, 6664, 6672, 研究論文（学術雑誌）, 10.1021/ic100673b

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• 査読無し, 英語, CHEMISTRY LETTERS, 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., 2010年04月, 39, 4, 332, 333, 研究論文（学術雑誌）, 10.1246/cl.2010.332

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2010年01月, 132, 1, 61, +, 研究論文（学術雑誌）, 10.1021/ja907460b

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• 査読無し, 英語, BIOCHEMISTRY, 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., 2010年01月, 49, 1, 49, 57, 研究論文（学術雑誌）, 10.1021/bi9017285

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2009年09月, 131, 34, 12394, 12405, 研究論文（学術雑誌）, 10.1021/ja904635n

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2009年06月, 131, 23, 8040, 8048, 研究論文（学術雑誌）, 10.1021/ja809183z

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• 査読無し, 英語, Inorg. Chem., Effect of Imidazole and Phenolate Axial Ligands on the Electronic Structure and Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complexes: Drastic Increase in Oxo-Transfer and Hydrogen Abstraction Reactivities, 藤井 浩; 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., 2009年03月, 48, 6, 2614, 2625, 研究論文（学術雑誌）, 10.1021/ic802123m

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• 査読無し, 英語, BIOCHEMISTRY, 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., 2009年02月, 48, 5, 898, 905, 研究論文（学術雑誌）, 10.1021/bi802030a

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• 査読無し, 英語, JOURNAL OF SYNCHROTRON RADIATION, 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., 2009年01月, 16, 110, 115, 研究論文（学術雑誌）, 10.1107/S0909049508034596

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• 査読無し, 英語, Chemistry Letters, ENDOR Study of Oxoiron(IV) Porphyrin π-Cation Radical Complexes as Models for Compound I of Heme Enzymes, 藤井 浩; 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., 2009年01月, 38, 1, 68, 69, 研究論文（学術雑誌）, 10.1246/cl.2009.68

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• 査読あり, 英語, LXIII YAMADA CONFERENCE ON PHOTO-INDUCED PHASE TRANSITION AND COOPERATIVE PHENOMENA (PIPT3), 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年, 148, 012035, 研究論文（国際会議プロシーディングス）, 10.1088/1742-6596/148/1/012035

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2008年09月, 47, 17, 7556, 7567, 研究論文（学術雑誌）, 10.1021/ic800443q

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2008年05月, 130, 19, 6088, 6098, 研究論文（学術雑誌）, 10.1021/ja075575b

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2008年03月, 47, 5, 1674, 1686, 研究論文（学術雑誌）, 10.1021/ic702061y

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• 査読無し, その他, 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年, 43, 11, 7, 18
• 査読無し, 英語, Inorg. Chem., Activation Parameters for Cyclohexene Oxygenation by an Oxoiron(IV) Porphyrin π-Cation Radical Complex: Entropy Control of an Allylic Hydroxylation Reaction, 藤井 浩; 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., 2007年08月, 46, 16, 6227, 6229, 研究論文（学術雑誌）, 10.1021/ic7009379

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2007年01月, 46, 2, 541, 551, 研究論文（学術雑誌）, 10.1021/ic060745r

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2006年09月, 45, 19, 7709, 7721, 研究論文（学術雑誌）, 10.1021/ic060650p

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2006年08月, 45, 17, 6816, 6827, 研究論文（学術雑誌）, 10.1021/ic0607383

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• 査読無し, 英語, JOURNAL OF INORGANIC BIOCHEMISTRY, 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., 2006年04月, 100, 4, 533, 541, 研究論文（学術雑誌）, 10.1016/j.jinorgbio.2006.01.009

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• 査読無し, 英語, BIOCHEMISTRY, 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., 2006年02月, 45, 8, 2515, 2523, 研究論文（学術雑誌）, 10.1021/bi051989a

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• 査読無し, 英語, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Spectroscopic characterization of reaction intermediates in a model for copper nitrite reductase, M Kujime; H Fujii, 2006年, 45, 7, 1089, 1092, 研究論文（学術雑誌）, 10.1002/anie.200503555

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• 査読無し, 英語, JOURNAL OF BIOLOGICAL CHEMISTRY, 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., 2005年11月, 280, 44, 36833, 36840, 研究論文（学術雑誌）, 10.1074/jbc.M503529200

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 2005年10月, 44, 22, 8156, 8166, 研究論文（学術雑誌）, 10.1021/ic051377e

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• 査読無し, 英語, TETRAHEDRON LETTERS, 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., 2005年04月, 46, 16, 2809, 2812, 研究論文（学術雑誌）, 10.1016/j.tetlet.2005.02.122

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Essential amino acid residues controlling the unique regioselectivity of heme oxygenase in Pseudomonas aeruginosa, H Fujii; XH Zhang; T Yoshida, 2004年04月, 126, 14, 4466, 4467, 研究論文（学術雑誌）, 10.1021/ja031791l

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2003年12月, 125, 52, 16340, 16346, 研究論文（学術雑誌）, 10.1021/ja037037e

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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, 2003年12月, 125, 52, 16208, 16209, 研究論文（学術雑誌）, 10.1021/ja038923s

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• 査読無し, 英語, BIOCHEMISTRY, 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., 2003年06月, 42, 24, 7418, 7426, 研究論文（学術雑誌）, 10.1021/bi027173g

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• 査読無し, 英語, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 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年, 42, 9, 1005, +, 研究論文（学術雑誌）, 10.1002/anie.200390256

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• 査読あり, 英語, PARAMAGNETIC RESONANCE OF METALLOBIOMOLECULES, 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年, 858, 97, 112, 研究論文（学術雑誌）
• 査読あり, 英語, PHYSICS LETTERS B, 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., 2002年10月, 545, 1-2, 82, 90, 研究論文（学術雑誌）
• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, C-13 NMR signal detection of iron-bound cyanide ions in ferric cyanide complexes of heme proteins, H Fujii, 2002年05月, 124, 21, 5936, 5937, 研究論文（学術雑誌）, 10.1021/ja025737y

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• 査読無し, 英語, COORDINATION CHEMISTRY REVIEWS, 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., 2002年03月, 226, 1-2, 51, 60, 研究論文（学術雑誌）, 10.1016/S0010-8545(01)00441-6

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2002年02月, 124, 8, 1798, 1808, 研究論文（学術雑誌）, 10.1021/ja0122391

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• 査読無し, 英語, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 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年, 41, 19, 3638, 3641, 研究論文（学術雑誌）, 10.1002/1521-3773(20021004)41:19<3638::AID-ANIE3638>3.0.CO;2-#

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• 査読無し, その他, 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年, 53, 18, 24
• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2001年07月, 123, 27, 6475, 6484, 研究論文（学術雑誌）, 10.1021/ja010490a

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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, 2000年08月, 122, 34, 8311, 8312, 研究論文（学術雑誌）, 10.1021/ja0002868

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 2000年05月, 122, 17, 4068, 4076, 研究論文（学術雑誌）, 10.1021/ja992219n

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• 査読無し, 英語, CHEMISTRY LETTERS, 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., 2000年03月, 3, 198, 199, 研究論文（学術雑誌）, 10.1246/cl.2000.198

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Resonance raman spectra of legitimate models for the ubiquitous compound I intermediates of oxidative heme enzymes, K Czarnecki; Kincaid, JR; H Fujii, 1999年09月, 121, 34, 7953, 7954, 研究論文（学術雑誌）, 10.1021/ja991712w

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• 査読無し, 英語, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 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., 1999年09月, 473, 1-2, 75, 84, 研究論文（学術雑誌）, 10.1016/S0022-0728(99)00287-9

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1999年08月, 38, 17, 3857, 3862, 研究論文（学術雑誌）, 10.1021/ic990328x

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• 査読無し, 英語, Biochim. Biophys. Acta, Molecular oxygen oxidizes the porphyrin ring of the ferric α-hydroxyheme in heme oxygenase in the absence of reducing equivalent, 藤井 浩; Catharina Taiko Migita; Hiroshi Fujii; Kathyn Mansfield Matera; Sataoshi Takahashi; Hong Zhou; Tadashi 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., 1999年07月, 1432, 2, 203, 213, 研究論文（学術雑誌）, 10.1016/S0167-4838(99)00097-7

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1999年04月, 38, 7, 1543, 1547, 研究論文（学術雑誌）, 10.1021/ic981369g

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1999年03月, 38, 6, 1276, 1281, 研究論文（学術雑誌）, 10.1021/ic981184+

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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, 1998年08月, 120, 32, 8251, 8252, 研究論文（学術雑誌）, 10.1021/ja973925w

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1998年06月, 37, 12, 3066, 3070, 研究論文（学術雑誌）, 10.1021/ic970138r

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1998年05月, 37, 10, 2405, 2414, 研究論文（学術雑誌）, 10.1021/ic9801241

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• 査読無し, 英語, JOURNAL OF BIOLOGICAL CHEMISTRY, 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., 1998年02月, 273, 8, 4317, 4322, 研究論文（学術雑誌）, 10.1074/jbc.273.8.4317

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• 査読無し, 英語, J. Am. Chem. Soc., Raman Signature of the Fe2O2 “Diamond” Core, 藤井 浩; Elizabeth C. Wilkinson; YangHong Dong; Yan Zang; Hiroshi Fujii; Robert Fraczkiewicz; Grazyna Fraczkiwicz; Roman; S. Czernuszewicz; d Lawrence Que, J, 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., 1998年02月, 120, 5, 955, 962, 研究論文（学術雑誌）, 10.1021/ja973220u

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• 査読無し, 英語, JOURNAL OF BIOLOGICAL CHEMISTRY, 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., 1998年01月, 273, 2, 945, 949, 研究論文（学術雑誌）, 10.1074/jbc.273.2.945

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• 査読あり, 英語, OXYGEN HOMEOSTASIS AND ITS DYNAMICS, 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年, 1, 304, 314, 研究論文（国際会議プロシーディングス）
• 査読あり, 英語, OXYGEN HOMEOSTASIS AND ITS DYNAMICS, 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年, 1, 315, 321, 研究論文（国際会議プロシーディングス）
• 査読無し, 英語, Inorg. Chem., Imidazole and p-Nitrophenolate Complexes of Oxoiron(IV) Porphyrin π-Cation Radicals as Models for Compounds I of Peroxidase and Catalase, 藤井 浩; Hiroshi Fujii; Tetsuhiko Yoshimura; Hitoshi Kamada, 1997年12月, 36, 27, 6142, 6143, 研究論文（学術雑誌）, 10.1021/ic970271j

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 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., 1997年07月, 119, 27, 6284, 6291, 研究論文（学術雑誌）, 10.1021/ja970602r

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• 査読無し, 英語, INORGANIC CHEMISTRY, 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., 1997年03月, 36, 6, 1122, 1127, 研究論文（学術雑誌）, 10.1021/ic960722k

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• 査読無し, 英語, Tetrahedron Letter, Regioselective Pyrrole Synthesis from Asymmetric β-Diketone and Conversion to Sterically Hindered Porphyrin, 藤井 浩; Hiroshi Fujii; Tetsuhiko Yoshimura; Hitoshi 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., 1997年02月, 38, 8, 1427, 1430, 研究論文（学術雑誌）, 10.1016/S0040-4039(97)00039-7

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• 査読無し, 英語, Biochemsitry, Resonance Raman Spectroscopic Characterization of α-Hydroxyheme and Verdoheme Complexes of Heme oxygenase, 藤井 浩; Satoshi Takahashi; Kathryn Mansfield Matera; Hiroshi Fujii; Kazunobu Ishikawa; Tadashi Yoshida; Masao Ikeda-Saito; Denis L. 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., 1997年02月, 36, 6, 1402, 1410, 研究論文（学術雑誌）, 10.1021/bi962361q

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• 査読無し, その他, 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年, 67, 128, 10.1016/S0162-0134(97)80008-6

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• 査読無し, 英語, J. Am. Chem. Soc., Resonance Raman Spectrum of a 2A1u Ferryl Porphyrin π-Cation Radical, 藤井 浩; Kazimierz Czarnecki; L. M. Proniewicz; Hiroshi Fujii; James R. Kincaid, 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., 1996年05月, 118, 19, 4680, 4685, 研究論文（学術雑誌）, 10.1021/ja954044x

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• 査読無し, 英語, Inorg. Chem., EPR Studies of A1u and A2u Oxoiron(IV) Porphyrin π-Cation Radical Complexes. Spin Coupling between Ferryl Iron and A1u /A2u orbitals, 藤井 浩; Hiroshi Fujii; Tsuhiko Yoshimura; Hitoshi 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., 1996年04月, 35, 8, 2373, 2377, 研究論文（学術雑誌）, 10.1021/ic9513752

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• 査読無し, 英語, J. Biol. Chem., Oxygen and One Reducing Equivalent Are Both Required for the Conversion of α-Hydroxyhemin to Verdoheme in Heme Oxygenase, 藤井 浩; Kathryn Mansfield Matera; Satoshi Takahashi; Hiroshi Fujii; Zhou Hong; Kazunobu Ishikawa; Tetsuhiko Yoshimura; Denis L. Rousseau; Tadashi Yoshida; Masao Ikeda-Saito, 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., 1996年03月, 271, 12, 6618, 6624, 研究論文（学術雑誌）, 10.1074/jbc.271.12.6618

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• 査読無し, 英語, THIN SOLID FILMS, 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., 1996年02月, 273, 1-2, 250, 253, 研究論文（学術雑誌）, 10.1016/0040-6090(95)06790-6

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• 査読無し, 英語, CHEMISTRY LETTERS, 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年, 8, 581, 582, 研究論文（学術雑誌）, 10.1246/cl.1996.581

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• 査読無し, 英語, J. Am. Chem. Soc., A High-Valent Nonheme Iron Intermediate. Structure and Properties of [Fe2(µ-O)2(5-Me-TPA)2](ClO4)3, 藤井 浩; Yanhong Dong; Hiroshi Fujii; Michael P. Hendrich; Randolph A. Leising; Ganfeng Pan; Clyton R. Randall; Elizabeth C. Wilkinson; Yan Zang; Lawrence Que, Jr; Brian G. Fox; Karl Kauffmann; Eckard Münck, 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., 1995年03月, 117, 10, 2778, 2792, 研究論文（学術雑誌）, 10.1021/ja00115a013

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• 査読無し, 英語, Inorg. Chem., Studies of the Iron(II) meso-Oxyporphyrin π-Neutral Radical as a Reaction Intermediate in Heme Catabolism, 藤井 浩; Isao Morishima; Hiroshi Fujii; Yoshitsugu Shiro; Seiyo 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., 1995年03月, 34, 6, 1528, 1535, 研究論文（学術雑誌）, 10.1021/ic00110a035

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• 査読無し, 英語, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH, CARBOXYLATOIRON(II) AGGREGATES - A NOVEL FE-4(II) COMPLEX WITH THREEFOLD SYMMETRY, S MENAGE; H FUJII; MP HENDRICH; L QUE, 1994年09月, 33, 15-16, 1660, 1662, 研究論文（学術雑誌）
• 査読無し, 英語, CHEMISTRY LETTERS, 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., 1994年08月, 8, 1491, 1494, 研究論文（学術雑誌）, 10.1246/cl.1994.1491

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• 査読無し, 英語, J. Am. Chem. Soc., Effects of the Electron-Withdrawing Power of Substituents on the Electronic Structure and Reactivity in Oxoiron(IV) Porphyrin π-Cation Radical Complexes, 藤井 浩, 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., 1993年06月, 115, 11, 4641, 4648, 研究論文（学術雑誌）, 10.1021/ja00064a027

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• 査読無し, 英語, Inorg. Chem., Characterization and Intramolecular Spin Coupling of a Monomeric a1u Copper(II) Porphyrin π-Cation Radical, 藤井 浩, 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., 1993年03月, 32, 6, 875, 879, 研究論文（学術雑誌）, 10.1021/ic00058a021

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• 査読無し, 英語, Inorg. Chem., Preparation and Characterization of an A1u Oxoiron(IV) Porphyrin π-Cation-Radical Complex, 藤井 浩; Hiroshi Fujii; Kazuhiko Ichikawa, 1992年03月, 31, 6, 1110, 1112, 10.1021/ic00032a039

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• 査読無し, 英語, J. Am. Chem. Soc., NMR Studies of Iron(II) Nitrosyl π-Cation Radicals of Octaethylchlorin and Octaethylisobacteriochlorin as Models for Reaction Intermediate of Nitrite Reductase, 藤井 浩; Shinji Ozawa; Hiroshi Fujii; Isao Morishima, 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., 1992年02月, 114, 5, 1548, 1554, 研究論文（学術雑誌）, 10.1021/ja00031a002

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• 査読無し, 英語, Inorg. Chem., Spin Coupling in Ferric Porphyrin and Chlorin π-Cation Radical Complexes, 藤井 浩; Satoru Nakashima; Hiroaki Ohya-Nishiguchi; Noboru Hirota; Hiroshi Fujii; Isao Morishima, 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., 1990年12月, 29, 26, 5207, 5211, 研究論文（学術雑誌）, 10.1021/ic00351a014

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• 査読無し, 英語, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, NMR-STUDIES OF METALLOPORPHYRIN RADICALS - IRON(II) OXOPHLORIN RADICAL FORMED FROM IRON(III) MESO-HYDROXYOCTAETHYLPORPHYRIN, MORISHIMA, I; H FUJII; Y SHIRO; S SANO, 1986年06月, 108, 13, 3858, 3860, 10.1021/ja00273a067

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• 査読あり, その他, 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, 2021年03月, 60, 3207, 3217, 研究論文（学術雑誌）
• 査読あり, その他, 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, 2021年07月, 111542, 研究論文（学術雑誌）
• 査読あり, その他, 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, 2021年07月, 60, 9243, 9247, 研究論文（学術雑誌）
• 査読あり, その他, 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, 2021年12月, 60, 17687, 17698, 研究論文（学術雑誌）
• 査読あり, その他, ACS Catalysis, 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, 2022年09月02日, 12, 17, 10857, 10871, 研究論文（学術雑誌）, 10.1021/acscatal.2c01840

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• 査読あり, その他, ACS Catalysis, 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, 2023年03月27日, 4842, 4852, 研究論文（学術雑誌）, 10.1021/acscatal.2c06122

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• 査読あり, その他, 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, 2023年04月
• 査読あり, その他, ChemSusChem, 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., 2023年10月, 研究論文（学術雑誌）, 10.1002/cssc.202300958

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• 査読あり, その他, Catalysis Science & Technology, 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., 2023年09月21日, 13, 18, 5280, 5289, 研究論文（学術雑誌）, 10.1039/d3cy00758h

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• その他, Journal of Inorganic Biochemistry, Resonance Raman study of oxoiron(IV) porphyrin π-cation radical complex: Porphyrin ligand effect on ν(Fe=O) frequency, Kaho Ueda; Wataru Sato; Sachiko Yanagisawa; Minoru Kubo; Masahiko Hada; Hiroshi Fujii, 2024年06月, 255, 112544, 112544, 研究論文（学術雑誌）, 10.1016/j.jinorgbio.2024.112544

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MISC

• 査読無し, その他, Journal of Computer Chemistry, Japan, Society of Computer Chemistry, Japan, 高スピンFe(IV)ポルフィリン錯体による オレフィンの エポキシ化反応：CASPT2の理論研究, 宇梶 かすみ; 阿部 穣里; 波田 雅彦; 藤井 浩, 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年, 13, 3, 167, 168, 10.2477/jccj.2014-0022

  DOI URL
• 査読無し, 日本語, 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, 2013年01月12日, 26th, 96

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• 査読無し, 日本語, 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年, 1st, 43

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• 査読無し, 日本語, 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年, 29th, 66

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• 査読無し, 日本語, 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, 2010年03月12日, 90th, 2, 268

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• 査読無し, 日本語, 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年, 27th, 89

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• 査読無し, 日本語, 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年, 4th, ROMBUNNO.3B13 (WEB ONLY)

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• 査読無し, 日本語, 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年, 3rd, ROMBUNNO.1B14 (WEB ONLY)

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• 査読無し, 日本語, 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, 2008年08月05日, 21st, 58, 59

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• 査読無し, 英語, 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年, 128, 48, 48, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 2003年07月, 96, 1, 133, 133, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 2000年03月, 219, U822, U822, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 1999年03月, 217, U1053, U1053, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 1997年09月, 214, 281, INOR, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 1997年09月, 214, 413, INOR, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 1996年02月, 70, 2, WP342, WP342, 研究発表ペーパー・要旨（国際会議）
• 査読無し, 英語, 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, 1987年06月, 106, 6-7, 334, 334, 研究発表ペーパー・要旨（国際会議）
• 英語, 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年, 64, C204, C205, 研究発表ペーパー・要旨（国際会議）, 10.1107/S0108767308093446

  DOI URL
• 日本語, 固体物理, アグネ技術センタ-, 金属酵素の反応中間体の電子状態・構造解析 (生物物質科学--金属を含む分子系を中心に 特集号) -- (生体分子系), 城 宜嗣; 藤井 浩, 2008年11月, 43, 11, 699, 710

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書籍等出版物

• 化学実験テキスト　第6版
• 錯体化合物辞典, 朝倉書店, FeN4OCl, 2019年, その他, その他
• Heme Peroxidases, Royal Society of Chemistry, 2016年, その他, 査読無し, その他
• クライトン「生物無機化学」, 東京化学同人, 2016年, その他, 査読無し, その他
• フロンティア 生物無機化学, 三共出版, 2016年, その他, 査読無し, その他
• 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年, その他, 査読無し, その他
• Paramagnetic Resonance of Metallobiomolecules, ACS Book Series 858, American Chemical Society, 2003年, その他, 査読無し, その他
• Paramagnetic Resonance of Metallobiomolecules, ACS Book Series 858, American Chemical Society, 2003年, その他, 査読無し, その他
• Metal-Oxo and Metal-Peroxo Species in Catalytic Oxidations, Structure & Bonding 97, Springer, 2000年, その他, 査読無し, その他
• Metal-Oxo and Metal-Peroxo Species in Catalytic Oxidations, Structure & Bonding 97, Springer, 2000年, その他, 査読無し, その他
• Oxygen Homeostasis and Its Dynamics, Springer, 1997年, その他, 査読無し, その他
• Oxygen Homeostasis and Its Dynamics, Springer, 1997年, その他, 査読無し, その他

講演・口頭発表等

• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• International Symposium on Reactive Intermediates and Unusual Molecules, Participation of Electron-Transfer process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2017年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• International Symposium on Reactive Intermediates and Unusual Molecules, Participation of Electron-Transfer process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2017年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 8th Asian Biological Inorganic Chemistry Conference (Asbic8), Mechanism of Aromatic Hydroxylation Reactions by Compound I of Cytochrome P450, 2016年, その他
• 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年, その他
• 8th Asian Biological Inorganic Chemistry Conference (Asbic8), Mechanism of Aromatic Hydroxylation Reactions by Compound I of Cytochrome P450, 2016年, その他
• 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年, その他
• 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年, その他
• 227th Electrochemistry Society Meeting, Role of the Heme Axial Ligand on the Reactivity of High-Valent Oxoiron(IV) Porphyrin Intermediate, 2015年, その他
• RIKEN Symposium "Metals in Biology" in Wako, Mechanism of Aromatic Hydroxylation by Cytochrome P450 Compound I Model Complexes, 2015年, その他
• IUPAC-2015, How does the Heme Axial Ligand Controles the Reactivity of High-velent oxoiron intermediates?, 2015年, その他
• ChemComm Symposium, Preparation, characterization and Reactivity of Iron(III) Porphyrin Hypochlorite Complexes as Models for Reactive Intermediates in Haloperoxidase, 2015年, その他
• 2nd Japan-Germany Joint Symposium, How does the axial ligand control the reactivity of high-valent metal oxo complex?, 2015年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• Pacifichem2015, Molecular Mechanism of Heme Axial Ligand for Controlling the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2015年, その他
• Pacifichem2015, Electronic Structure of One-electron Oxidized Mixed-Valence Metal Salen Complexes, 2015年, その他
• 227th Electrochemistry Society Meeting, Role of the Heme Axial Ligand on the Reactivity of High-Valent Oxoiron(IV) Porphyrin Intermediate, 2015年, その他
• RIKEN Symposium "Metals in Biology" in Wako, Mechanism of Aromatic Hydroxylation by Cytochrome P450 Compound I Model Complexes, 2015年, その他
• IUPAC-2015, How does the Heme Axial Ligand Controles the Reactivity of High-velent oxoiron intermediates?, 2015年, その他
• ChemComm Symposium, Preparation, characterization and Reactivity of Iron(III) Porphyrin Hypochlorite Complexes as Models for Reactive Intermediates in Haloperoxidase, 2015年, その他
• 2nd Japan-Germany Joint Symposium, How does the axial ligand control the reactivity of high-valent metal oxo complex?, 2015年, その他
• Pacifichem2015, Molecular Mechanism of Heme Axial Ligand for Controlling the Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2015年, その他
• Pacifichem2015, Electronic Structure of One-electron Oxidized Mixed-Valence Metal Salen Complexes, 2015年, その他
• 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年, その他
• 41st International Conference on Inorganic Chemistry, Hypochlorito-rion(III) Porphyrin Complexes as Models for Reaction Intermediates of Catalytic and Biological Reactions, 2014年, その他
• 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年, その他
• 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年, その他
• 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年, その他
• 41st International Conference on Inorganic Chemistry, Hypochlorito-rion(III) Porphyrin Complexes as Models for Reaction Intermediates of Catalytic and Biological Reactions, 2014年, その他
• 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年, その他
• 16th International Conference on Bioinorgnaic Chemsitry, Synthesis, Characterization, and Reactivity of Hypochlorite-Iron(III) Porphyrin Complexes, 2013年, その他
• 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年, その他
• 4th Asian Conference on Coordination Chemistry, Structure and Reactivity of Iodosylarene Adduct of Manganese(IV) Salen Complex, 2013年, その他
• 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年, その他
• 16th International Conference on Bioinorgnaic Chemsitry, Synthesis, Characterization, and Reactivity of Hypochlorite-Iron(III) Porphyrin Complexes, 2013年, その他
• 4th Asian Conference on Coordination Chemistry, Structure and Reactivity of Iodosylarene Adduct of Manganese(IV) Salen Complex, 2013年, その他
• 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, 2020年11月07日, その他
• 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, 2020年03月23日, その他
• 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, 2020年03月23日, その他
• 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, 2019年11月19日, その他
• 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, 2019年11月09日, その他
• 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, 2019年11月09日, その他
• 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, 2019年11月09日, その他
• 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, 2019年09月22日, その他
• 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, 2019年09月22日, その他
• 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, 2019年09月21日, その他
• 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, 2019年09月21日, その他
• 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, 2019年09月05日, その他
• 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?, 2019年08月25日, その他
• Hiroshi Fujii, International Conference on Bioinspired Small Molecule Activation, Heterolytic versus Homolytic Bond Cleavage of Hypochlorite by Iron(III) Porphyrin Complexes, 2019年06月07日, その他
• 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, 2019年03月16日, その他
• Hiroshi Fujii, 9th Asian Biological Inorganic Chemistry Conference (Asbic9), Critical Factors in Determining the Reactivity of Hypochlorite Adducts of Metal Complexes, 2018年12月09日, 2018年12月14日, その他
• 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？, 2018年11月10日, その他
• 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, 2018年11月01日, 2018年11月02日, その他
• 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, 2018年11月01日, 2018年11月02日, その他
• 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, 2018年11月01日, 2018年11月02日, その他
• 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, 2018年11月01日, 2018年11月02日, その他
• 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, 2018年09月09日, 2018年09月11日, その他
• 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, 2018年09月09日, 2018年09月11日, その他
• 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, 2018年08月04日, 2018年08月05日, その他
• Hiroshi Fujii, 43rd International Conference on Coordination Chemistry, Heterolytic versus Homolytic Bond Cleavage of Hypochlorite by Iron Porphyrin Complexes, 2018年07月31日, 2018年08月04日, その他
• Kana Nishikawa; Yuki Honda; Hiroshi Fujii, 43rd International Conference on Coordination Chemistry, Disproportionation of Metal(IV) Oxo Complexes, 2018年07月31日, 2018年08月04日, その他
• 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, 2018年07月28日, 2018年07月30日, その他
• 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, 2018年07月28日, 2018年07月30日, その他
• Hiroshi Fujii, 10th International Conference on Porphyrins and Phthalocyanines, Participation of Electron-Transfer Process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2018年07月01日, 2018年07月06日, その他
• 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, 2018年06月26日, その他
• Hiroshi Fujii, 2018 Korea-Taiwan-Japn Bioinorganic Chemistry Symposium, Participation of Electron-Transfer Process in Aromatic Hydroxylation Reactions by Heme Enzymes, 2018年05月31日, その他
• Hiroshi Fujii, 11th International Conference on Porphyrins and Phthalocyanines, What is an essential factor for determining the bond cleavage process of hemebound terminal oxidant?, 2021年07月28日, その他
• 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, 2021年10月31日, その他
• 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, 2021年10月31日, その他
• Hiroshi Fujii, Pacifichem 2021, Cytochrome P450 compound I prefers hydroxylation of hydrocarbon rather than epoxidation of olefin, 2021年12月20日, その他
• Hiroshi Fujii, Pacifichem 2021, Factors controlling the formation and disproportionation of high-valent oxoiron porphyrin complexes, 2021年12月19日, その他
• Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, How do the porphyrin and axial ligands regulate the formation and reactivity of Compound I?, 2022年12月02日, その他
• 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, 2022年11月29日, その他
• 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, 2022年11月29日, その他
• Nozomi Nakatani; Yuki Honda; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Disproportionation of Oxomanganese(IV) and Oxochromium(IV) Porphyrin Complexes, 2022年11月29日, その他
• Kaho Ueda; Yuki Honda; Hiroshi Fujii, 10th Asian Biological Inorganic Chemistry Conference, Mechanism of Sulfoxidation Catalyzed by Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2022年11月29日, その他
• 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, 2022年11月05日, その他
• 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, 2022年11月05日, その他
• 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, 2022年11月05日, その他
• 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, 2022年11月05日, その他
• 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, 2022年10月21日, その他
• 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, 2022年09月25日, その他
• 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, 2022年09月25日, その他
• Hiroshi Fujii, 8th International Conference on Coordination Chemistry, Molecular Mechanisms Controlling Formation and Reactivity of Oxoiron(IV) Porphyrin π-Cation Radical Complex, 2022年08月09日, その他
• 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, 2022年06月18日, その他
• 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, 2022年06月18日, その他
• Hiroshi Fujii, 23rd International Conference on Cytochrome P450 (ICCP450), Molecular Mechanism Controlling Formation and Reaction Steps of Compound I, 2023年09月29日, 2023年09月26日, 2023年09月29日, その他
• 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, 2024年03月20日, その他
• 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, 2023年11月11日, その他
• 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, 2023年11月11日, その他
• 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？, 2023年11月11日, その他
• 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, 2023年11月11日, その他
• 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, 2023年09月26日, その他
• 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, 2023年09月26日, その他
• 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, 2023年09月26日, その他
• 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, 2023年09月08日, その他
• 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, 2023年09月04日, その他

共同研究・競争的資金等の研究課題

• 基盤研究B, 2022年04月, 2025年03月, 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
• 基盤研究B, 2022年04月, 2025年03月, 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
• 2019年04月, 2022年03月, 研究代表者, 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, 競争的資金
• 2016年10月, 2023年03月, 研究代表者, 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, 競争的資金
• 2017年04月, 2020年03月, 研究代表者, 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, 競争的資金
• Reactivity and selectivity of metalloenzymes relating to biological oxidation reactions, 0, 0, 0, 競争的資金
• 基盤研究(B), 2017年04月01日, 2020年03月31日, 17H03032, 次亜塩素酸と金属錯体の反応を支配する機構の解明とそれに基づく酵素機能変換法の開発, 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, 18590000, 14300000, 4290000, 次亜塩素酸イオンの開裂様式について研究を行った。次亜塩素酸イオンの開裂過程は、その後に生成する反応活性種の性質を決定する重要な過程である。本研究では、ヘム錯体と次亜塩素酸イオンとの反応を低温で種々の分光法を用いて研究をした。その結果、次亜塩素酸イオンの開裂様式を支配する機構の解明に成功した。この機構は、次亜塩素酸イオン以外の他の酸化剤の結合開裂様式を予測できる一般性の高い機構であることが証明できた。さらに金属イオンに配位した次亜塩素酸イオンの反応性を制御する機構の解明にも成功した。アキシャル位とエクアトリアル位の配位子効果を統合的に説明できる機構を提案することができた。, kaken

  対象リソースIRI
• 基盤研究(B), 2004年, 2006年, 16350094, 立体構造にもとづく基質結合サイトの再構築による酵素反応選択性の制御, 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), 15600000, 15600000, 本研究では、ヘムオキシゲナーゼというヘム代謝を行う酵素を研究題材にして、酵素反応選択性を人工的に自在に変換することをめざした。ヘムには、酸化的解裂反応を受けうる部位が4つ存在する。それらはα、β、γ、δメソ位と呼ばれている。化学的にヘムを分解すると、これら4つの部位がそれぞれ解裂した4種類の異性体をほぼ同じ当量で生成する。しかし自然界のヘムオキシゲナーゼは、αメソ位が解裂した異性体のみしか生成しないことが知られている。本研究では、ヘムオキシゲナーゼがもつαメソ位選択性の機構に基づき、反応させたいメソ部位が活性点近傍に来るようにヘムオキシゲナーゼの活性中心を再構築して、反応選択性を自在制御した。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。ヘムを酵素内で90度反時計回りに回転させ。α選択性を示すヘムオキシゲナーゼをδ選択性の酵素へと変換することに成功した。ヘムの回転は、NMRや酵素のX線構造解析から証明することができた。また、ヘムの配向を制御することにより、本来選択性をもたない酵素からβ選択性とδ選択性をもつ酵素をそれぞれ作成することができた。本研究の成果は、ヘムオキシゲナーゼの反応選択性を自在に制御できることを実験的に示しただけでなく、ヘムオキシゲナーゼの反応選択性の機構をより明確にし、今後この手法がより多くの酵素に適応できる新しい概念になる可能性を示したものであると考える。, kaken

  対象リソースIRI
• 特定領域研究, 2005年, 2005年, 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
• 基盤研究(B), 2002年, 2003年, 14340212, 非ヘム単核酵素反応中間体としての高原子価鉄オキソ錯体の合成と反応性の研究, 藤井 浩; 倉橋 拓也, 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, 15000000, 15000000, 生体には鉄イオンを活性中心にもつ非ヘム酵素が数多く存在し、生命活動を支えている。これらの酵素の中で酸素分子を活性化して酸化反応を行う酵素は、その反応中に高酸化状態の反応中間体を生成すると考えられている。さまざまな研究の結果、この反応中間体は鉄5価オキソ錯体あるいは、鉄4価オキソ錯体であると考えられている。しかしこれまで多くの研究が行われてきたにもかかわらず、鉄5価オキソ錯体や鉄4価オキソ錯体を単離した報告はなく、またモデル錯体の合成例もなかった。我々は、高原子価状態を安定化する配位子としてサレン配位子に着目して、酵素反応中間体としての高原子価鉄オキソ錯体の合成、およびその反応性の解明をめざした。5配位型鉄3価アクア錯体、ヒドロキシ錯体をサレンから初めて合成することができた。これらの錯体の構造を解析した結果、サレン配位子ではこれまでに報告のない三角両錐構造をとることがわかった。この構造は、カテコールを酸化する酵素の活性中心と類似することもわかった。また、この三角両錐構造はアクア配位子の電子的効果による構造変化であることが明らかとなった。さらに、この新規サレン配位子を用いて、鉄錯体の合成を行った。この錯体を低温中酸化することにより、緑色の反応中間体を生成することに成功した。この中間体は、酵素反応中間体モデルになる可能性を示した。そこで、この緑色中間体の電子状態をEPR、NMR、メスバウアーなどの分光法を用いて検討した。その結果、配位子が可逆的に酸化された鉄3価フェノキシラジカル錯体であることが明らかとなった。これまで、鉄錯体の酸化において配位子が酸化される例は数少なく、今回の錯体は興味深い。また今回の結果は、酵素反応中間体を検討する上で、配位環境の重要性を示すものと考える。, kaken

  対象リソースIRI
• 特定領域研究, 2001年, 2003年, 13125208, ヘムを基礎とする高機能複合たんぱく質の創製とその支援研究, 島田 秀夫; 藤井 浩; 林 高史; 向井 邦晃; 菱木 貴子; 江川 毅, 日本学術振興会, 科学研究費助成事業, 慶應義塾大学, 40600000, 40600000, 膜蛋白質複合体の発現系構築:ヘムを基礎とする高機能複合たんぱく質の創製とその支援的研究の一環として、ミトコンドリア(mt)のウシチトクロム酸化酵素の発現系を構築した。本酵素は、核とmtにそれぞれエンコードされる多数のサブユニットからなる。最大サブユニットであるmt由来サブユニットI(SI)が本酵素機能に必須だが、ヒトHeLa細胞核に、強力なプロモーター支配下のウシSI遺伝子を組み込み、細胞質で発現したSIをmtに輸送させ、ウシSIとヒト由来サブユニットからなる雑種チトクロム酸化酵素発現系を開発した。雑種酵素はヒト本来の酵素と遜色ない酸素還元活性と、それに共役したプロトンポンプ活性をもつ。宿主内には、純粋のヒト酵素が共存するが、雑種酵素が圧倒的に多く発現する。本発現系を用い、プロトンポンプの鍵アミノ酸残基を見いだすとともに、ポンプ能のみ失活した酵素を作製し、二つの機能が分離可能なことを実証した。今回開発した方法は、mt由来膜蛋白質変異に起因したミトコンドリア機能障害の治療に適応可能なため、新規ミトコンドリア病の遺伝子治療法の開発に発展する。また大腸菌の無細胞タンパク合成系で、外来的に補欠分子族ヘムを加え、土壌細菌Paracoccus denitrificansチトクロム酸化酵素を機能発現させた。本発現系により、高度に疎水的な膜蛋白質に外来性ヘム導入が可能となった。 化学修飾ヘムを用いた高機能触媒体の創製:ミオグロビン(Mb)の活性中心ヘムを特定の機能を発揮するように化学修飾をデザインし、酸素保存体であるMbにmonooxygenase活性、peroxygenase活性、peroxidase活性をそれぞれ付与できた。また活性中心ヘムを非天然ポルフィセン(ポルフィリン鉄錯体の構造異性体)に置換し、酸素親和性を1000倍に増大させとともに、蛋白部分の改変と組み合わせ、非常に高い酸化活性を発揮させた結果、環境ホルモンをきわめて効率よく酸化分解した。以上の成果は、高機能触媒体の創製に化学修飾ヘムなど非天然ヘム導入が極めて有効であることを示す。今回の研究成果は、本研究グループによる蛋白質改変と非天然ヘム導入を組み合わせた高機能触媒体の創製法が、高度に疎水的膜蛋白質複合体を基礎とする新規触媒体開発研究に適応可能なことを示した。, kaken

  対象リソースIRI
• 基盤研究(C), 2000年, 2001年, 12680625, ヘムオキシゲナーゼ反応における酸素活性化と構造との関連, 吉田 匡; 藤井 浩; 張 旭紅, 日本学術振興会, 科学研究費助成事業, 山形大学, 3700000, 3700000, 1。ジフテリア菌のヘムオキシゲナーゼ(HmuO)とヘムとの結合にはHmuOのヒスチジン20残基の中性イミダゾール基が関与していることをEPR、共鳴ラマンスペクトルの実験から明らかにした。このことは還元型のH20A変異酵素の共鳴ラマンの結果からも証明された。第五配位子を欠き、酵素活性もないH20A変異酵素にイミダゾールを加えたところ、ヘム分解活性が回復した。従って、H20Aでヘム分解活性を欠くのは第五配位子が欠如しているためと結論された。 2。ヘムオキシゲナーゼ(HO)反応ではαビリベルジンのみが選択的に生成する。しかし、ラットHO-1の183番のアルギニンをカルボキシル基を持つグルタミン酸やアスパラギン酸に変えるとα型の他に20%程度のδ型が生ずることが判明した。これはおそらく、変異酵素での183番目ののカルボキシル基とヘムのプロピオン酸基との相互作用によってα特異性が崩れたためと考えられた。 3。ヘムポケットを構成するアスパラギン酸140(D140)をアラニンやアスパラギンに変えた変異酵素ではヘム分解反応が野生型に比べ低下していた。特に過酸化水素による反応では、野生型はベルドヘムまで分解されるのに対し、D140AではコンパウンドIIで停止した。1)140のカルボキシル基が酸素活性化のために必須の役割を持つと判断された。 4。ラットのビリベルジン還元酵素の結晶化と構造解析に成功した。本酵素は二つのドメインから成り、N末端側のドメインはNADPHやNADHを認識するヌクレチオド結合モチーフを持っており、C末端側にはβシート構造が多く見られた。これらの構造を本にNADPHやビリベルジンの結合部位を推測できた。, kaken

  対象リソースIRI
• 基盤研究(C), 2000年, 2001年, 12640549, 合成ヘムとミオグロビン変異体による亜硝酸還元酵素モデルの構築と反応機構の研究, 藤井 浩; 船橋 靖博, 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, 3700000, 3700000, 脱窒過程の一部を担うヘム型亜硝酸還元酵素の反応機構を解明するため、その酵素モデルの作成を行った。本酵素は、ジケト型イソバクテリオクロリンをその活性中心にもつ。そこで、化学的にジケト型イソバクテリオクロリンの合成を行った。ポルフィリンを出発原料としてオスミウム酸化によりモノケト型クロリンとした後、異性体を分離後、もう一度オスミウム酸化を行いジケト型イソバクテリオクロリンを合成することができた。得られたジケト型イソバクテリオクロリンに鉄イオンを挿入した。得られた鉄錯体は、アポミオグロビンに1:1で取り込まれ、安定な複合体を形成できることがわかった。そこで、さらに触媒活性をもたせるため、ミオグロビンの変異体の作成を行った。亜硝酸還元酵素の活性中心と類似の構造をとるようにするため、ミオグロビンのヒスチジン-64をチロシンに変異させた。さらに、触媒活性をあげるため、ロイシン-29とフェニルアラニン-45をそれぞれヒスチジンに変異させた。3重ミュータントを大腸菌で発現させたところ、十分な発現量の変異型ミオグロビンを単離することができた。さらに、これをアポ化したのち、ジオキソイソバクテリオクロリン鉄錯体と複合体を生成させた。カラム分離後、種々の分光学的性質を測定した結果、今回の変異ミオグロビン-ジオキソイソバクテリオクロリン複合体は、亜硝酸還元酵素の分光学的性質とよい一致を示した。これは、変異ミオグロビン-ジオキソイソバクテリオクロリン複合体が、亜硝酸還元酵素のモデル酵素になることを示し、当初の目的の一つを達成すことができた。さらに、このモデル酵素に亜硝酸イオンを添加したところ、鉄3価の活性中心に配位することがわかった。これは、酵素反応が鉄2価を経由して進行するというこれまでの提案とは異なる結果を示し、鉄3価での反応機構の可能性を示唆した。, kaken

  対象リソースIRI
• 基盤研究(B), 2000年, 2001年, 12480176, 細胞内シグナルトランスダクションを担うヘム関連タンパクの構造と機能, 齋藤 正男; 冨田 毅; 藤井 浩; 城 宜嗣; 松井 敏高; 広津 晶子, 日本学術振興会, 科学研究費助成事業, 東北大学, 2200000, 2200000, 本研究ではヘム分解酵素であるヘムオキシゲナーゼの研究を行った。まず高等動物由来の構成型ヘムオキシゲナーゼ(HO-2)の構造解析を行うために、大腸菌での大量発現系を利用してHO-2の高純度精製と結晶化条件のスクリーニングを実行した。その結果、これまでに知られている精製法ではHO-2の2量体などが含まれていることが明らかとなり、さまざまな改良を加えた精製法の開発により、現在考え得るレベルで最も純度の高い標品を得ることができるようになった。一方、バクテリア由来のヘムオキシゲナーゼ(HmuO)では大腸菌の大量発現系をもとに精製した試料を用いて結晶化することに成功していたので、HmuOの結晶構造解析に取り組むこととした。その実験に先立ち、可視吸収スペクトルや共鳴ラマンスペクトルなどの各種分光測定や、酵素反応解析などの基本的な酵素科学的性質をHO-2、HmuOについて調べた。それらの結果をもっともよく研究されている誘導型ヘムオキシゲナーゼ(HO-1)の結果と比較し、これらのタンパク質間ではヘム近傍の構造や酵素反応スキームが細かい点では異なっているものの、基本的には同一であることが確認された。HmuOのX線結晶構造解析においては、酸化型酵素の構造を1.4Åの分解能で、酸化型酵素を一電子還元した最初の中間体である還元型酵素の構造を1.7Åの分解能で、それぞれ決定することに成功した。この結果、ヘムの酸化還元に伴ってヘム周辺の酵素の構造が大きく変化することが明らかとなり、この構造変化によって作られる立体効果が、引き続き起こる酵素の結合と、その部位特異的な酸化反応に重要な役割を果たすことを示せた。また、本構造解析により、反応に必要なプロトンの取り込み機構に関しても新たな知見を得ることが出来、重要な成果となった。, kaken

  対象リソースIRI
• 特定領域研究(A), 1999年, 1999年, 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
• 基盤研究(A), 1998年, 1999年, 10044233, ヘムオキシゲナーゼによるヘムの分解機構, 吉田 匡; 藤井 浩; 佐藤 道比古; 張 旭紅; 右田 たい子; OLSOH John S, 日本学術振興会, 科学研究費助成事業, 山形大学, 9400000, 9400000, 1.ヘムオキシゲナーゼ(HO)-2の近位リガンドの同定の為,His45残基をAlaに置換した変異酵素を作成した.この酵素はヘム分解活性を全く持たず,更にNOが結合した還元型ヘム・HO複合体は五配位であった.故に,His45が近位His残基であることが確定した.2.ヘム・HO複合体の酸素とCOへの親和性を検討した.一般にCOは酸素に較べてより高い親和性を持っているが,ヘム・HO複合体の場合には酸素の親和性が非常に高かった.本反応で生成されるCOによる阻害が何故起らないか,その理由が明らかになった.3.酸素化型コバルトヘム・HO複合体のEPR測定実験から,酸素分子はヘムポケットのH供給体と水素結合を作り安定化されていることが更に明白になった.4.ヘミンからαヒドロキシヘミンヘの反応では活性化された酸素の分子種はFe-OOHと推測されてきた.それを証明するために酸素化型HO複合体を作り,それに低温(77k)でγ線を照射して還元したところ,Fe-OOHのシグナルが現れ,次いでヒドロキシヘミンに転換した.これはFe-OOHが活性化酸素の実体である決定的な証拠である.5.ヒドロキシヘミンからベルドヘムヘの段階では酸素分子の他に一当量の電子が不可欠という報告を1996年にしている.然し,その後電子は不要という異論も出た.それゆえ,あらためて詳細に検討した.酸素だけではヒドロキシヘムはそのポルフィリン環が酸化されたラジカルになるだけであり,ベルドヘムの転換にはやはり電子が必須であった.6.Corynebacterium diphtheriaeのヘム分解酵素であるHmuOの大腸菌での発現系と精製法を確立した.HmuOは単純蛋白質であるが基質であるヘムを1対1で結合して出来た複合体は単純蛋白質の性質を持っていた.ヘムは基質であると共に酸素活性化の役割も持ち,ヘム自身は自触的反応により,αヒドロキシヘミン,ベルドヘム,ビリベルジン・鉄錯塩を経てピリベルジン迄分解された.HmuOは基本的には動物系のHOと似ているが,細部では異なる点も観察され,この点の解明が今後の課題である., kaken

  対象リソースIRI
• 特定領域研究(A), 1998年, 1998年, 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年, 1998年, 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
• 基盤研究(B), 1997年, 1998年, 09480158, ヘムオキシゲナーゼ反応における三段階での酵素活性化の分子機構, 吉田 匡; 右田 たい子; 藤井 浩; 張 旭紅, 日本学術振興会, 科学研究費助成事業, 山形大学, 2800000, 2800000, 1.ヘム分解反応の二つの中間体であるヒドロキシヘム或はベルドヘムとヘムオキシゲナーゼ(HO)複合体の共鳴ラマン解析を行いその特性を明らかにし,これら中間体での酸素活性化機構解明の手掛かりを得た.2.HO-2のHis45をAlaに換えた変異酵素ではヘム分解活性は全く消失していた.更に,EPRの結果からHis45が近位Hisであることを明らかにした.His152は酵素活性発現には全く関与していなかった.この結果は私共のHO-1での結果,即ちHO-2のHis152に相当するHO-1のHis132をAlaに換えた変異酵素の諸性質は野性型酵素と同であった,とも矛盾しない.3.本反応ではCOが生成するがこのCOによってヘム分解反応が阻害されるようすが無い.その理由を検討したところ,ヘム鉄への酸素親和性が異常に高く,CO親和性と匹敵することが知られた.本反応で生じるCO濃度は反応場では酸素濃度より低いのでCOは阻害出来ないものと思われる.4.ヘム鉄に結合した酸素分子はFe-O-O-Hとなってから二つの酸素原子間が切断されると考えられてきた.恐らく,ヘム鉄に結合した酸素分子はヘムポケットのアミノ酸残基と水素結合を作り,次いでFe-O-O-Hとなるものと考えられる.コバルトプロトポルフィリンとHOとの酸素化型複合体についてEPR解析を行った結果それを証明出来た., kaken

  対象リソースIRI
• 重点領域研究, 1997年, 1997年, 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年, 1997年, 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
• 国際学術研究, 1996年, 1997年, 08044240, ヘムオキシゲナーゼによるヘム分解反応の分子機構, 吉田 匡; 周 虹; OLSON John S; SAITO Masao; 右田 たい子; 藤井 浩; 兪 善昌; ROUSSEAU Den; IKEDAーSAITO マサオ; 野口 正人, 日本学術振興会, 科学研究費助成事業, 山形大学, 11200000, 11200000, 1.ヘムオキシゲナーゼ(HO)によるヘム分解反応の二つの中間体であるヒドロキシヘム或はベルドヘムとヘムオキシゲナーゼ複合体の共鳴ラマン解析を行いその特性を明きらかにし,これら中間体での酸素活性化機構解明の手掛かりを得た.2.HO-2のHis45をAlaに換えた変異酵素(H45A)ではヘム分解活性は全く消失していた.更にEPRの結果からHis45が近位Hisであることを明きらかにした.His152は米国の研究者により遠位Hisと報告されたが,私共の実験ではこのHisは酵素活性発現には全く関与していなかった.この結果は私共のHO-1での結果,つまりHO-2のHis152に相当するHO-1のHis132をAlaに換えた変異酵素の諸性質は野性型酵素と全く同であった,とも矛盾していない.His152Alaは大腸菌では封入体として発現されていた.恐らく彼らはmisfoldingあるいはunfoldingした酵素が混入した資料を用いたのではないかと思われる.3.本反応ではCOが生成するがこのCOによってヘム分解反応が阻害される様子がない.その理由を検討したところ,ヘム鉄への酸素親和性は異常に高く,CO親和性と匹敵することが知られた.本反応で生ずるCO濃度は反応場では酸素濃度よりも低いので,COは本反応を阻害できないものと思われる.4.ヒドロキシヘムからベルドヘムヘの反応では一電子が必須であることを咋年報告した.然し,これには電子は不必要という異論が米国の研究者から出された.それゆえ,再度詳細に検討したがやはり一電子は不可欠であった.私共は化学合成したヒドロキシヘムを用いたのに対し,彼らはヘムそのものから出発しているために,結果の違いが出たものと思われる., kaken

  対象リソースIRI
• 基盤研究(C), 1996年, 1996年, 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年, 1996年, 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年, 1995年, 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), 2022年04月01日, 2025年03月31日, 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
• 基盤研究(B), 2013年04月01日, 2017年03月31日, 25288032, 次亜塩素酸錯体の反応性と反応選択性の分子機構の解明及びそれに基づく制御法の開発, 藤井 浩; 波田 雅彦; 小倉 尚志; 足立 伸一, 日本学術振興会, 科学研究費助成事業, 18720000, 14400000, 4320000, 本研究では、酸化反応や生体防御過程の鍵となる次亜塩素酸錯体の生成機構や反応性に関する研究を行った。次亜塩素酸の生成過程を解明するため、酵素活性中間体モデル化合物を合成し、それと塩素イオンとの反応を研究した。その結果、次亜塩素酸を合成する酵素がもつ活性部位のシステイン配位やヘムとアミン酸の共有結合によるひずみが次亜塩素酸生成反応の鍵となっていることを明らかにした。次亜塩素酸錯体の反応性を解明するため、シス位とトランス位の配位子の電子供与性効果を研究した。その結果、シス位配位子とトランス位配位子の効果が反応性に対して逆の傾向を示すというたいへん興味深い結果を得ることができた。, kaken

  対象リソースIRI
• 基盤研究(B), 2010年, 2012年, 22350030, 高原子価オキソ金属錯体の反応性と反応選択性を制御する分子機構の解明, 藤井 浩; 倉橋 拓也; 波田 雅彦, 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(岡崎共通研究施設), 19370000, 14900000, 4470000, 本研究では、様々な酸化反応の活性種となる高原子価オキソ錯体や酸化剤付加錯体の反応性や反応選択性が、どのような因子により制御されているのかを研究した。高原子価オキソ錯体の代表として鉄4価オキソポルフィリンπカチオンラジカル錯体に着目し、そのアキシャル位の配位子による新たな反応性制御機構を実験的に解明した。また反応選択性を研究するため、不斉マンガンサレン触媒に着目し、そのマンガン4価ヨードソアレン付加錯体の合成、単離、構造解析に成功した。これにより新たな不斉選択性機構を提案した, kaken

  対象リソースIRI
• 基盤研究(B), 2010年, 2012年, 22350010, 相対論的 SAC-CI を中核とする磁気的分子物性と励起状態反応系に関する理論研究, 波田 雅彦; 長谷川 淳也; 藤井 浩, 日本学術振興会, 科学研究費助成事業, 首都大学東京, 16770000, 12900000, 3870000, 本研究プロジェクトの主目的は、重原子を含む化合物において、電子励起状態が関与する化学現象を定量的に解析するための理論的方法として高次相対論を含めたSAC-CI法の開発を進め、例えば、光化学反応の解析、スピン-軌道(SO)相互作用や交換交差など考慮した定量的なエネルギー曲面の記述、など実施することであった。SO-CASSCF法では化学的精度の達成は困難であるため、本研究では、Generalized UHFを参照としたCCSD法からSAC-CI理論と同等の方法GUHFCCSD-CIによって励起状態を計算する理論を提案し、その計算プログラムを作成した。幾つかの原子の励起エネルギーを計算することでこの理論・方法の精度を検討した。原子の一重項、三重項の最低励起エネルギーを、本方法と、RHFを参照するSAC-CI法と、CASPT2法で計算した。他の計算方法と比較して、本方法GUHF-CCSD-CIが、三重項励起に対する分裂の実験値を格段に良く再現していた。更に、相対論補正が重要となる幾つかの応用計算を実施した。(i)冷却分子を用いて新たな量子物性探査を支援するため、MgLi, CaLi, SrLi, BaLi分子における電子基底状態のPESとPDMをCCSD(T)法で求め、 v=0における放射寿命は短いもので22秒であった。これは冷却分子実験の時間スケールに対して十分に長く、物性測定の可能性を示唆した。(ii)鉛原子を含んだ5員環化合物Plumboleに、 THF、 Py、 NHCが配位した化合物の芳香族性や、 C-NMR, Pb-NMRの特徴について研究した。 NICSの観点からは対象分子が芳香属性をもつことを示した。通常は重原子に隣接する軽原子は高磁場シフトするのだが、Pbに隣接するC13-NMRはPbのSpinOrbit相互作用の影響を受けて低磁場シフトすることを示した。, 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）

• 日本化学会生体関連化学部会, 幹事, 2017年04月, 9999年, 日本化学会生体関連化学部会, 学協会
• 日本化学会, 代議員, 2022年10月, 9999年, 学協会
• 日本化学会生体関連化学部会, 幹事
• 日本化学会, 代議員