2006 Fiscal Year Final Research Report Summary
Mechanistic Evaluation and Application of Dioxygen Activation by Copper Proteins
| Project/Area Number |
17350086
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Chemistry related to living body
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| Research Institution | Osaka City University |
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Principal Investigator |
ITOH Shinobu Osaka City University, Graduate Sccool of Sciencer Department of Chemistry, Professor, 大学院理学研究科, 教授 (30184659)
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| Co-Investigator(Kenkyū-buntansha) |
TACHI Yoshimitsu Osaka City University, Graduate Sccool of Science, Department of Chemistry, Research Assistant, 大学院理学研究科, 助手 (50336757)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Copper Protein / Hemocyanin / Tyrosinase / Oxygenation Reaction / Dioxygen Activation / Enzymatic Reaction Mechanism / Copper-Dioxygen Complex / Active Oxygen Species |
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| Research Abstract |
Model studies as well as biological studies have been carried out to evaluate and apply the chemical functions of mononuclear and dinuclear copper proteins involved in the biological dioxygen processing such as reversible dioxygen binding and activation. The followings are the results obtained in this project.
1) Evaluation of Oxidation Ability of Mononuclear and Dinuclear Copper-Active Oxygen Complexes
A series of alkylamine ligands that can effectively support mononuclear and dinuclear copper-active oxygen species have been designed and synthesized, and copper(I) complexes of those ligands have been prepared. The crystal structures as well as redox potentials of the copper(I) complexes have been explored, and their reactivity toward molecular oxygen has been investigated in detail. Based on the several spectroscopic features of the resulting copper-dioxygen adduct, the binding mode of O_2 to the copper ion (side-on vs. end-on) has been explored. Then, the reactivity of the copper-dioxy
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gen complexes, both self-decomposition reaction leading ligand hydroxylation reaction and oxidation and/or oxygenation of external substrates, have been studied extensively by means of detailed product analysis including isotope-labeling experiment and systematic kinetic studies including kinetic isotope effects. Those studies have provided significantly important insights into the intrinsic reactivity and the reaction mechanisms of the copper-dioxygen complexes. Similar studies have been carried out using copper(II) complexes as the starting materials and hydrogen peroxide and alkylhydroperoxide as the oxidant to find a formation of novel copper(II)-alkylperoxo complex which exhibit excellent aromatic hydroxylation ability.
2) Oxygenation Ability of Type-3 Copper Proteins
Oxygenation of a series of p-substituted phenols to the corresponding catechols (phenolase activity) by the (μ-η^2:η^2-peroxo)dicopper(II) species of Octopus hemocyanin has been directly examined for the first time by using a UV-vis spectroscopic method in a 0.5 M borate buffer solution containing 8 M urea under anaerobic conditions. Preliminary kinetic studies have indicated that the reaction involves electrophilic aromatic substitution mechanism as in the case of phenolase reaction of tyrosinase. Less
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