Primary Electron Transfer Processes in Photosynthetic Bacterial Reaction Centers

细菌反应中心（RC）是膜结合的色素-蛋白质复合物，光能在这里转化为化学势能。这种转化是通过一系列快速和高度特异的电子转移反应发生的，这些反应使电荷在膜上分离，量子产率为100%。这项工作的最终目标是在分子水平上对初级电荷分离过程有一个全面的了解。为此，跨越飞秒到秒时间尺度的瞬态吸收光谱测量以及其他光谱技术将用于直接探测电荷分离的中间状态及其形成和衰变的速率。研究将集中在位点导向突变包含一个或多个突变附近的辅助因子。许多尚未解决的问题将被解决，包括特定发色团在电子转移途径中的参与，电子转移的方向性通过两条平行传递链（L和M）之一的起源，以及确保电荷分离速率和竞争性电荷重组过程速率之间有利平衡的因素。本研究的总体目标是了解细菌光合作用中初级电荷分离过程的分子机制。本研究揭示的原理也适用于其他生物反应中心的初级光化学，包括植物中的PSII。最后，该研究应积极影响生物物理学中更广泛的主题，包括生物电子转移和静态和动态蛋白质在调节其辅因子的功能特性中的作用。＊＊＊

9723008 Holten The bacterial reaction center (RC) is the membrane-bound pigment-protein complex where light energy is converted into chemical potential energy. This conversion occurs via a series of fast and highly specific electron transfer reactions that separate charge across the membrane with a quantum yield of (100%. The ultimate goal of this work is to arrive at a comprehensive understanding of the primary charge separation process at the molecular level. To this end, transient absorption spectroscopic measurements spanning the femtosecond to seconds time scales as well as other spectroscopic techniques will be used to directly probe the intermediate states of charge separation and the rates of their formation and decay. The research will focus on site-directed mutants containing one or more mutations near the cofactors. Numerous unresolved issues will be addressed, including the involvement of specific chromophores in the pathway of electron transfer, the origin of the directionality of electron transfer via one of two parellel transport chains (L and M), and the factors that ensure the favorable balance between the rates of charge separation and the rates of competing charge recombination processes. The overall goal of this research is to understand the molecular mechanisms of the primary charge separation process in bacterial photosynthesis. The principles uncovered by this research should also apply to the primary photochemistry in reaction centers from other organisms, including PSII in plants. Finally, the research should positively impact broader topics in biophysics including biological electron transfers and the role of a protein, both static and dynamic, in modulating the functional properties of its cofactors. ***