Mechanism and Macromolecular Organization in Photosynthetic Reaction Centers

光合反应中心的机理和大分子组织

• 批准号: 9205004
• 负责人: Steven Boxer
• 金额: $ 35.8万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-08-01 至 1996-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9205004&HistoricalAwards=false
• 关键词: Mechanism; Macromolecular; Organization; Photosynthetic; Reaction

In order to understand the mechanism of the initial charge separation steps in bacterial photosynthetic reaction centers, several lines of investigation are proposed. (i) Measurements of the resonance Raman intensities and excitation profile for the lowest Qy electronic state of the special pair, combined with photochemical holeburning, absorption and electroabsorption (Stark effect) spectroscopy, to obtain information on excited state dynamics; (ii) preparation and characterization of site-specific mutants in the vicinity of the special pair which perturb its redox properties to obtain information on the local dielectric properties which may affect unidirectional electron transfer; and (iii) studies of the quantum yields and kinetics of RC mutants whose donor, acceptor and mediating state redox properties are different from wild-type in applied electric fields to determine the mechanism of the fast charge separation and slower charge recombination reactions. %%% Photosynthetic reaction centers are the smallest chlorophyll- protein complex capable of sustaining the light-induced charge separation reactions which initiate photosynthesis. The first reactions are among the fastest reactions known in any system. In addition to the obvious importance of these reactions as the primary source of stored chemical energy on earth, these reactions have much broader biophysical and chemical significance. This is because electron transfer reactions are ubiquitous in nature, and because of the relative simplicity of this type of reaction, there is some prospect of being able to understand the reaction mechanism at a fundamental level. Bacterial reaction centers were the first membrane protein to be characterized by x-ray crystallography, and consequently all of our work falls under the general heading of structure-function relationships. The proposed research focuses on systematically altering the rates and mechanisms of charge-transfer reactions in the reaction center by modifying either internal or external electric fields. Internal fields can be altered by changing specific amino acids or stretches of amino acids using recombinant DNA methods. External fields can be applied either with electrodes to a bulk sample or as transmembrane potentials. The latter are of very great importance in nearly all biological assemblies and we seek to understand the mechanisms which couple such potentials to biological function.

为了理解初始电荷的机制 在细菌光合反应中心的分离步骤， 提出了几条调查路线。 (i)测量 的共振拉曼强度和激发分布， 特殊对的最低Qy电子态，结合 光化学空穴燃烧、吸收和电吸收（Stark 效应）光谱，以获得关于激发态的信息 动态;（二）特定地点的准备和表征 突变体在附近的特殊对扰乱其氧化还原 特性以获得关于局部介电特性的信息 其可影响单向电子转移;和（iii） 研究RC突变体的量子产率和动力学， 供体、受体和介导态的氧化还原性质不同 从野生型在施加电场，以确定 快电荷分离慢电荷机理 重组反应 %%% 光合作用反应中心是最小的叶绿素- 能够维持光诱导电荷的蛋白质复合物 引发光合作用的分离反应。 第一 反应是已知的任何系统中最快的反应之一。 在 除了这些反应的明显重要性外， 这些反应是地球上储存的化学能的主要来源， 具有更广泛的生物物理和化学意义。 这是 因为电子转移反应在自然界中无处不在， 由于这种类型的反应相对简单， 是理解反应机理的前景 在一个基本的层面上。 细菌反应中心是第一个 通过X射线晶体学表征膜蛋白，和 因此，我们所有的工作福尔斯都属于总的标题下， 结构-功能关系。 拟议的研究重点是 系统地改变电荷转移的速率和机制 反应中心的反应，通过改变内部或 外部电场。 内部字段可以通过以下方式更改： 改变特定的氨基酸或氨基酸片段， 重组DNA方法。 外部字段可以应用于 用电极对大量样品或作为跨膜电位。 后者在几乎所有生物学中都非常重要。 我们试图了解这些组合的机制， 这种潜在的生物功能。