Theory and Calculations of Electron Transfer in Protein Media

(1)以光合细菌反应中心的细菌嗜铬蛋白阴离子与伯奎宁的电子转移为例，采用分子动力学模拟和量子化学相结合的方法，研究了蛋白质环境中电子转移的机理。(2)We发现ET速率的电子隧穿矩阵元根据蛋白质构象的热涨落而变化几个数量级。(3)我们发现，大的变化的起源主要是氨基酸构象的波动，而不是给体-受体距离的波动。(4)我们发现存在两条主要的隧穿路径，它们的隧穿电流方向相反，导致了大量的破坏性量子干涉。(5)We发展了一种新的非康登理论，该理论适用于ET的电子因子变化非常快的情况。因此，我们推导出的公式描述的ET率作为两项之和：第一个是由于弹性电子隧穿机制，其中电子能量是保存之前和之后ET的ET率。这一机制与普通的ET理论相一致。第二个是由于非弹性电子隧穿机制的ET率，其中电子能量在ET之前和之后不守恒。吸收或发射的能量是由于电子隧穿矩阵元涨落的傅里叶变换的频率。(6)通过数值计算，我们发现非弹性隧穿机制在Marcus能隙定律的实质反转区域起作用。(7)我们发明了一种新的方法，通过适当地平均涨落来获得平均隧穿路线，涉及到量子干涉效应的影响。

(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.