Mechanism and Macromolecular Organization in Photosynthetic Reaction Centers

9506178 Boxer该研究资助继续支持光合细菌反应中心（RC）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：（i）通过共振拉曼和高阶斯塔克光谱探测引发电荷分离的特殊对初级电子给体1 P的激发态的性质;（ii）通过对通过基因工程修饰或去除组分的RC的测量来区分一步和两步电子转移;（iii）电场调制来自1 P的自发荧光，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，电偶极矩的形成与1 P衰变竞争;（四）通过转化使功能特异性的残基，研究包含P的细菌叶绿素分子与蛋白质环境之间的相互作用与P相互作用成甘氨酸，创建空腔，可以结合外源有机分子，以调节光合功能;和（v）的起源，单向电子转移探测的基础上测量的介电不对称性和进化分析的定点诱变。 光合RCs中的初始电子传递事件是地球上生命各个方面所必需的关键能量转换和储存机制。无论是在分子水平上还是从更全局的角度，对这一系统的研究都可以为改善自然光合作用和模拟人工光合作用提供方法。光合机构主要是一个膜蛋白复合物，其结构阐明在过去的10年中，第一次提供了有关膜蛋白的折叠和组织的信息。很可能在未来5年内，光合作用膜的整体结构将被完全表征，这是生物学上独特的重大成就。光合蛋白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范例，从而极大地影响了分子尺度电子器件的思维和前景。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特性，以及叶绿素型分子与其蛋白质环境之间的相互作用，这些环境调节这些发色团的特性并独特地确定电子流的方向。 ***

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. ***