| Project/Area Number |
05453030
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Organic chemistry
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| Research Institution | KYUSHU UNIVERSITY (1994)
Okazaki National Research Institutes (1993) |
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Principal Investigator |
NARUTA Yoshinori Kyushu Univ., Inst.Fund.Res.Org.Chem.Prof., 有機化学基礎研究センター, 教授 (00108979)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥7,500,000 (Direct Cost: ¥7,500,000)
Fiscal Year 1994: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1993: ¥6,700,000 (Direct Cost: ¥6,700,000)
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| Keywords | Metalloporphyrin / Catalase / Oxygen evolving complex / Water oxidation / Manganese / Electron transfer / 過酸化水素 / マンガン錯体 / ポルフィリン / チトクロームP‐450 / 両面修飾ポルフィリン / 酸素分子活性化 / マンガンカタラーゼ / マンガンポルフィリン |
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| Research Abstract |
Metalloenzymes play versatile roles in biological systems. Most of them have not well-characterized on their structures and reaction mechanisms. Especially, the instability of the enzymes is the major obstacle to elucidate them. In this research project, we have studied modeling of (1) electron transporting system in cytochrome c_3, and (2) manganesecontaining enzymes involved in oxygen evolving processes : bacterial manganese catalase (Mn-CAT) and oxygen evolving complex (OEC) in PSII of higher plants and cyanobacteria. Athracene-linked porphyrin dimers and tetramer can form the corresponding 'imidazoratesqueezed' complexes, which indicated large antiferromagnetic coupling between the Fe (III) ions and negative shifts on their reduction potential. These compounds are considered to be good models of cytochrome c_3. Next, we studied on the modeling of manganese containing enzymes, which involve manganese catalases and oxygen evolving complex in chloroplast. Both of them have function to evolve O_2. To construct their functional model to mimic the oxygen evolution, we used manganese porphyrins, which were considerably stable at their higher oxidation states and showed characteristic UV-vis spectrum depending upon their oxidation states. In the disproportionation of H_2O_2, we found the optimum Mn-Mn separation to attain high catalase activity to be 4.0 A.Such manganese porphyrin dimers also have catalytic activity on the evolution of O_2 by four-electron oxidation of water. This is the first example of the catalytic oxidation of water with use of manganese complexes possessing structurally well-defined structure.
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