Mechanism and Macromolecular Organization in Photosynthetic Reaction Centers

这项研究基金继续支持光合细菌反应中心（RCs）电荷分离和重组过程机制的生物物理研究。解决这些问题的具体方法包括：(1)利用共振拉曼光谱和高阶斯塔克光谱探测特殊对初级电子供体1P的激发态性质，从而引发电荷分离；（ii）通过对通过基因工程修饰或去除组分的RCs进行测量来区分一步和两步电子转移；（iii）对来自1P的自发荧光进行电场调制，以确定电场是否影响初级电荷分离步骤和电偶极矩的方向，其形成与1P衰变相竞争；（iv）研究含磷细菌叶绿素分子与蛋白质环境之间的相互作用，将与磷进行功能特异性相互作用的残基转化为甘氨酸，形成可以结合外源有机分子调节光合功能的空腔；(v)基于介电不对称测量和进化分析的位点特异性诱变技术探测单向电子转移的起源。光合作用RCs中的初始电子转移事件是地球上生命各个方面所必需的关键能量转导和储存机制。对该系统的研究，无论是从详细的分子水平还是从更全局的角度，都可以为改进自然光合作用和模拟人工光合作用提供途径。光合机构主要是一个膜蛋白复合物，在过去的10年里，其结构的阐明首次提供了关于膜蛋白折叠和组织的信息。很可能在未来5年内，光合膜的整体组织将被完全表征，这是生物学上独特而重大的成就。光合蛋白质中的电子转移为理解纳米尺度上控制电子快速运动的因素提供了一个范例，从而极大地影响了分子尺度电子器件的思考和前景。本研究的重点是了解最早的光驱动电子转移反应的机制，导致有效电荷分离的独特激发态性质，以及叶绿素型分子与其蛋白质环境之间的相互作用，这些相互作用调节了这些发色团的性质并独特地决定了电子流的方向。＊＊＊

9506178 Boxer This research grant funds continued support for biophysical studies of the mechanism of charge separation and recombination processes in reaction centers (RCs) from photosynthetic bacteria. The specific approaches to these problems include: (i) the nature of the excited state of the special pair primary electron donor, 1P, which initiates charge separation probed by resonance Raman and higher order Stark spectroscopies; (ii) distinguishing one step and two step electron transfer by measurements on RCs in which components are modified or removed by genetic engineering; (iii) electric field modulation of the spontaneous fluorescence from 1P to determine whether the field affects the primary charge separation step and the direction of the electric dipole moment whose formation competes with 1P decay; (iv) studies of the interaction between the bacteriochlorophyll molecules comprising P and the protein environment by converting residues which make functionally specific interactions with P into glycine, creating cavities which can bind exogenous organic molecules to modulate photosynthetic function; and (v) the origin of unidirectional electron transfer probed by site specific mutagenesis based both on measurements of dielectric asymmetry and an evolutionary analysis. %%% The initial electron transfer events in photosynthetic RCs are the key energy transduction and storage mechanisms essential for all aspects of life on earth. Studies of this system, both at the detailed molecular level and from a more global perspective, can offer approaches for improving natural photosynthesis and modeling artificial photosynthesis. The photosynthetic apparatus is largely a membrane protein complex whose structure elucidation over the past 10 years has provided, for the first time, information on the folding and organization of membrane proteins. It is likely that within the next 5 years, the overall organization of the photosynthetic membrane will be fully characteriz ed, a unique and major achievement in biology. Electron transfer in photosynthetic proteins provides a paradigm for understanding the factors that control the rapid movement of electrons on the nanometer scale, and thus have greatly influenced thinking and prospects for molecular scale electronic devices. This research focuses on understanding the mechanism of the earliest, light driven electron transfer reactions, the unique excited state properties that lead to efficient charge separation, and the interactions between the chlorophyll type molecules and their protein environment which modulate the properties of these chromophores and uniquely determine the direction of electron flow. ***