Effect of Protein Conformation Fluctuation on the Election Transfer Rate through Protein Media

一般来说，通过蛋白质介质的电子传递是一种远距离的电子传递，即通过隧道机制，通过感受蛋白质环境中的电气氛，从供体到受体发生电子传递。到目前为止，人们认为会有一个电子可能被转移的区域。通常化学键等被认为是它的候选者。如果发生这种情况，则由于蛋白质中的化学键不受蛋白质构象波动的影响，因此不会因蛋白质构象的热波动而对基质元素的选择产生较大的影响。然而，根据我们通过分子动力学模拟实现蛋白质构象波动和量子化学理论计算电子隧穿矩阵元素的研究结果，电子隧穿矩阵元素由于蛋白质的构象波动而发生了迅速而巨大的变化。对于其机理，认为隧穿电流的相位间干扰较大。事实上，电子隧穿矩阵元素中值的快速波动如何影响ET速率是一个非常有趣的问题。我们建立了一个新的非condon理论，在该理论中，我们可以使用经典MD模拟得到的电子隧穿矩阵元素的时间相关函数。在该理论中，对核运动进行了量子修正，从而满足了正反向速率的详细平衡条件。利用这一理论分析了蛋白质介质中的电子转移，发现电子隧穿矩阵元素的快速波动对ET速率的能隙依赖性有很大影响。即;研究发现，在远正向区和远倒向区均存在非弹性隧穿机制，因此在远正向区和远倒向区，蒸散率都得到了显著提高。我们调查了支持这一预测的实验数据。然后，我们发现在极性溶液中荧光猝灭的Rehm-Weller实验中，在非常大的能隙下，ET率没有明显的衰减，这与我们的理论一致：较少

Electron transfer (ET) through protein media is, in general, a long-range ET Namely, ETs take place from donor to acceptor by the tunneling mechanism, by feeling electric atmosphere from protein environment. So far, it was considered that there will be a region through which an electron is likely to be transferred. Usually chemical bonds and so on are considered as its candidate. If it happens, the election tunneling matrix element will not be changed considerably by the thermal fluctuation of protein conformation, because chemical bonds in the protein are not changed by the conformation fluctuation of protein. However, according to the results of our study in which protein conformation fluctuations are realized by the molecular dynamics (MID) simulation and electron tunneling matrix elements are calculated by the quantum chemical theory, electron tunneling matrix element is changed rapidly and greatly by the conformation fluctuation of proteins. As its mechanism, it is considered that … More interference among phases of tunneling currents works significantly. Indeed, it is a very interesting problem how the rapid fluctuation of the value in the electron tunneling matrix element affects the ET rate. We constructed a new non-Condon theory in which we can use the time correlation function of the electron tunneling matrix element obtained by the classical MD simulation. In this theory, the quantum, correction to the nuclear motion is performed and so, the detailed balance condition for the forward and backward rates is satisfied. As a result of analyzing the electron transfer in protein media using this new theory, we found that the energy gap dependence of the ET rate is greatly affected by the rapid fluctuation of the electron tunneling matrix element. Namely; we found that an inelastic tunneling mechanism works at the far normal region and far inverted region and then, the ET rates are much enhanced in both regions. We surveyed the experimental data which support this prediction. Then, we found that the ET rate does not decay appreciably at the very large energy gap in the Rehm-Weller experiment for the fluorescence quenching in polar solution, which is consistent with our theory: Less