2006 Fiscal Year Final Research Report Summary
Mechanistic Studies of Photoinduced Electron Transport across Vesicle Bilayers
| Project/Area Number |
16550030
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MURATA Shigeru The Univ.of Tokyo, Dep.of Arts and Sciences, Associate Prof., 大学院総合文化研究科, 助教授 (40192447)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Photoinduced electron transfer / Lipid bilayer membranes / Pyrene derivatives / Photoenergy conversion / Vesicles |
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| Research Abstract |
Endoergic electron transport across vesicle bilayers from ascorbate (Asc^-) in the inner waterpool to methylviologen (MV^<2+>) in the outer aqueous solution was driven by the irradiation of pyrene derivatives embedded in the vesicle bilayers. The initial rate of MV^<2+> reduction is dependent on the substituent group on the pyrenyl ring ; a hydrophilic functional group linked with the pyrenyl ring by a short methylene chain acts as a sensitizer for the electron transport. Mechanistic studies suggests that the electron transport is mainly initiated by the reductive quenching of the singlet excited state of pyrene by Asc^- and proceeds by a mechanism involving electron exchange between the pyrenes located at the inner and outer interface across the vesicle bilayer. Novel unsymmetrically substituted pyrenes having both a hydrophilic group linked by a short methylene chain and a hydrophobic long alkyl group was designed and synthesized, which acted as an excellent sensitizers for the electron transport across vesicle bilayers. Moreover, in order to enhance the electron transport efficiency, the effects of molecular structure of lipids and electron donors incorporated in the inner waterpool on the MV^<2+> reduction rate were investigated. The use of newly synthesized dimeric pyrenes bridged by a long alkyl chain as sensitizers resulted in the enhancement of electron transport efficiency. Although these systems unfortunately cannot work using visible light, it appears to be one of the most faithful model of natural photosynthesis in that an electron is transferred with the aid of light energy between two reversible redox couples in the energetically uphill direction through lipid bilayer walls preventing a charge recombination.
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