Electron and Proton Transfer in Photosynthetic Reaction Centers

该项目涉及电子和质子的机制 在光合作用的反应中心复合物中的转移 细菌，球形红细菌和绿色红细菌， 其中反应中心（RC）的结构在原子上是已知的 分辨率 主要的焦点是两个醌分子， 作为光化学反应的电子受体。 醌 进行单电子还原为半醌，并双 还原为醌醇状态，这也需要摄取 水介质中的质子。 这项工作的目的是确定氨基 在两种醌的结合中具有活性的酸残基， 稳定的半醌状态，在建立 两种醌的功能氧化还原电位，以及在 质子转移途径导致形成醌醇状态。 特定突变对功能性氧化还原和酸- 电子门的基本特性，以Rb为单位。威尔？斯菲罗伊德斯 通过动力学和平衡技术进行研究， 光谱学和电测量。 这些将是 辅以结构研究，包括X射线差异 分析（如可能）和红外光谱（FTIR），以及 计算方法，利用比较优势， 最大限度地发挥变异RC的作用 %%% 这项工作的主要目标是（1）展示和 了解特定的活动和属性是如何在 生物辅因子通过蛋白质-配体相互作用，和（2） 研究质子通过蛋白质转移的机制。 这些是酶催化中重要的一般问题， 生物特异性 反应中心的醌类化合物具有独特的 适合这些调查，通过伟大的实验， 生物物理测量系统的适用性， 蛋白质工程

This project addresses the mechanisms of electron and proton transfer in the reaction center complex of the photosynthetic bacteria, Rhodobacter sphaeroides and Rhodopseudomonas viridis, for which the structure of the reaction center (RC) is known at atomic resolution. The main focus is the two quinone molecules that act as electron acceptors to the photochemical events. The quinones undergo one-electron reduction to the semiquinone, and double reduction to the quinol state, which also requires uptake of protons from the aqueous medium. The work aims to identify amino acid residues active in the binding of both quinones, in the stabilization of the semiquinone states, in the establishment of the functional redox potentials of the two quinones, and in the proton transfer pathways leading to formation of the quinol state. The effects of specific mutations on the functional redox and acid- base properties of the to-electron gate, in Rb. Sphaeroides, will be investigated by kinetic and equilibrium techniques based on optical spectroscopy and electrometric measurements. These will be supplemented by structural studies, including X-ray difference analysis where possible, and infra-red spectroscopy (FTIR), and by computational approaches, utilizing the comparative virtues of mutant RCs to maximum effect. %%% The primary goals of this work are (1) to demonstrate and understand how specific activities and properties are induced in biological cofactors by protein-ligand interactions, and (2) to investigate the mechanism of proton transfer through proteins. These are important general issues in enzymatic catalysis and biological specificity. The reaction center quinones are uniquely suited for these investigations, through the great experimental amenability of the system for biophysical measurements and for protein engineering.