Mechanism and Macromolecular Organization in Photosynthetic Reaction Centers

本研究的目的是了解光合作用反应中心(RCS)中的电荷分离和复合机制以及光合膜的高级结构。为了理解电子转移机制，描述了几个领域：(I)在红外光谱中应用新开发的测量Stark效应的仪器和用于分析与氧化特殊对相关的价带间Stark效应的理论；(Ii)使用新开发的实验方法--共振Stark谱确定控制替代电子转移路径的参数；(Iii)将共振Stark方法应用于通过设计RC而创建的其他路径；(Iv)测量电场对光系统II RCS中电荷分离物种数量的影响，特别是类胡萝卜素的作用；以及(V)RC菌株的开发和应用，其中所有天然半胱氨酸残基被删除，并插入新的半胱氨酸作为不同类型标记的位点特异性靶标。为了了解光合膜的组织和组装，描述了几个方面：(I)天线蛋白复合体在支撑膜中的横向迁移率和组装的表征；(Ii)用原子力显微镜和一种新型的高横向分辨率的二次离子质谱仪对支撑脂质双层中的光合膜组分进行成像。本研究利用支持膜中的光合作用蛋白作为一种工具来发展成像和结构方法，并确定这一重要的膜相关组件的远程组织。通过整合这一系列方法，可以提高对初始电子转移机制和相关的单向电子转移现象的基本理解，并将其纳入复杂生物组件结构-功能关系的更大背景下。光合作用领域的研究解决了蛋白质中有组织的环境调节结合的假体基团和具有特殊功能结果的特定氨基酸功能基团的性质的机制这一普遍问题。这项工作的一个重要部分涉及开发新的实验和理论方法，这些方法可以对其他科学和技术领域产生广泛影响。几乎每一种光谱、结构和理论方法都被应用于Rc和光合膜功能的某些方面。在许多情况下，这是将新的物理方法应用于生物学问题的第一个例子，通常导致物理和理论方法的重大改进，这些概念和方法现在被用于许多其他领域。这一一般研究领域也是本科生、研究生和博士后研究员的巨大培训来源，通常是物理科学和生物学之间的桥梁。从最广泛的角度来看，光合作用研究的概念和结果已经影响到太阳能研究和新兴的分子电子学领域。

AbstractMCB 0416623The objective of this research is to understand the mechanisms of charge separation and recombination in photosynthetic reaction centers (RCs) and the higher-order organization of photosynthetic membranes. Towards understanding electron transfer mechanism, several areas are described: (i) application of newly developed instrumentation for measuring Stark effects in the IR and theory for analyzing intervalence band Stark effects associated with the oxidized special pair; (ii) determination of the parameters that control alternative electron transfer pathways using a newly-developed experimental method, resonance Stark spectroscopy; (iii) application of the resonance Stark method to other pathways created by engineering the RC; (iv) measurement of electric field effects on the populations of charge-separated species in photosystem II RCs, in particular the role of carotenoid cations; and (v) development and application of RC strains in which all native cysteine residues are deleted and new cysteines are inserted as site-specific targets for different types of labels. Towards understanding photosynthetic membrane organization and assembly several areas are described: (i) characterization of the lateral mobility and assembly of antenna protein complexes in supported membranes; and (ii) imaging of components of the photosynthetic membrane in supported lipid bilayers by atomic force microscopy and a novel type of secondary ion mass spectrometry with high lateral resolution. This research uses photosynthetic proteins in supported membranes both as a tool to advance imaging and structural methods and to determine the long-range organization of this important membrane-associated assembly.By integrating this range of approaches, the basic understanding of the mechanism of the initial electron transfer and the related phenomenon of unidirectional electron transfer can be advanced and brought into the larger context of structure-function relationships in complex biological assemblies. Research in the photosynthesis area addresses the general problem of the mechanisms by which the organized environment in proteins modulates the properties of bound prosthetic groups and particular amino acid functional groups with extraordinary functional consequences. An important part of this work involves the development of new experimental and theoretical methods that can have a broad impact in other areas of science and technology. Nearly every spectroscopic, structural, and theoretical method has been applied to some aspect of RC and photosynthetic membrane function. In many cases this was the first example of new physical approaches applied to a biological problem, often leading to significant improvements in the physical and theoretical methods, and these concepts and methods are now used in many other fields. This general area of research has also been a tremendous source of training for undergraduates, graduate students and postdoctoral fellows, often serving as a bridge between the physical sciences and biology. Viewed in broadest terms, concepts and results from photosynthesis research have impacted solar energy research and the emerging area of molecular electronics.