Primary Electron Transfer Processes in Photosynthetic Bacterial Reaction Centers

9723008细菌反应中心（RC）是膜结合的色素-蛋白质复合物，光能在此转化为化学势能。 这种转换通过一系列快速和高度特异性的电子转移反应发生，这些反应以100%的量子产率将电荷跨膜分离。 这项工作的最终目标是在分子水平上的主要电荷分离过程的全面理解。 为此，跨越飞秒至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减的速率。 这项研究将集中在含有一个或多个突变的辅助因子附近的定点突变。 许多悬而未决的问题将得到解决，包括参与特定的发色团， 电子转移的路径，通过两个平行的传输链（L和M）之一的电子转移的方向性的起源，以及确保电荷分离速率和竞争电荷重组过程的速率之间的有利平衡的因素。 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。 这项研究所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，研究应该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蛋白质的作用，静态和动态，在调节其辅助因子的功能特性。 ***

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. ***