2007 Fiscal Year Final Research Report Summary
Theory and Calculations of Electron Transfer in Protein Media
| Project/Area Number |
17570137
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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 |
Biophysics
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| Research Institution | Meijo University |
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Principal Investigator |
KAKITANI Toshiaki Meijo University, Department of Science and Technology, Professor (90027350)
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| Project Period (FY) |
2005 – 2007
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| Keywords | protein / electron transfer / tunneling route / tunneling cirrent / quantum interference / biophysics / biological energy transformation / photosynthesis |
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| Research Abstract |
(1) We investigated the mechanism of electron transfer (ET) in protein environment, by taking an example of ET of bacteriopheophitin anion to primary quinine in the reaction center of photosynthetic bacteria by the combined study of molecular dynamics simulations and quantum chemistry. (2)We found that electronic tunneling matrix element of the ET rate is varied by a few orders of magnitude according to the thermal fluctuation of the protein conformation. (3) We found that the origin of the large variation is mostly fluctuations of amino acid conformation rather than the fluctuation of donor-acceptor distance. (4) We found that there exist two main tunneling routes with opposite tunneling currents, bringing about a large amount of destructive quantum interference. (5)We developed a new non-Condon theory which is usable when the electronic factor of the ET is varied very quickly. As a result, we derived the formula describing the ET rate as a sum of the two terms: The first is the ET rate due to the elastic electron tunneling mechanism in which the electron energy is conserve before and after ET. This mechanism corresponds to the ordinary ET theory. The second is the ET rate due to the inelastic electron tunneling mechanism in which the electron energy is not conserved before and after ET. The absorbed or emitted energy is due to the frequency of Fourier transform for the fluctuation of electron tunneling matrix element. (6) By numerical calculations, we found that the inelastic tunneling mechanism works appreciably at the substantial inverted region of the Marcus energy gap law. (7) We invented a new method for properly averaging the fluctuation to obtain the average tunneling route, involving the effect of quantum interference effect.
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