Mechanism and Macromolecular Organization in Photosynthetic Reaction Centers

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本研究的目的是了解光合反应中心（RC）中的电荷分离和重组机制以及光合膜的高阶组织。 该研究项目侧重于三个领域：（一）电子转移的机制，在RC中的主要电子受体已被删除;（二）使用振动旁观者探针，以量化在RC静电;和（三）先进的成像技术的发展，使用定义明确的光合复合物和组件作为模型系统。 通过与正常电子转移被阻断的RC合作，可以在干净的背景下揭示新的途径，并捕获重要的中间体。 特别是，沿着RC的通常非功能侧的电子转移的动力学和能量学可以深入研究。 这个项目将研究一种被认为是调节反应能量学的特定氨基酸的方向。 一套方法将观众振动探针引入RC中，以测量静电场中与电子转移有关的位置的差异，以及当电子转移发生时场的探针变化。 区域（i）和（ii）集中在细菌光合作用中出现的特定的，明确定义的问题;结果和方法将适用于更复杂的光合生物和生物电子转移的广泛领域。 区域（iii）使用光合系统，但将影响新方法的发展，用于表征膜和膜蛋白一般。 成像质谱法将被推到其极限使用高度组织的光合作用膜，特别是看看是否可以可视化完整的膜蛋白质组织。 已经开发出一种“膜干涉仪”，它将先进的制造、膜组件和光学器件结合在一个对膜曲率和渗透压高度敏感的装置中。 光合作用蛋白将被用来测试这种干涉仪的精度，测试有关光合膜蛋白对膜曲率和出芽的影响的假设，并作为膜曲率的报告者，在这一领域的持续支持导致了许多新的方法的发展，用于研究电子转移反应，物理和生物系统中最重要的一类反应。 几乎每一个光谱，结构和理论方法已被应用到某些方面的RC和光合膜功能。 在许多情况下，这是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显着改进，这些概念和方法现在被用于许多其他领域。 RC在表面上的组装开辟了一个全新的技术领域，即膜图案化，该技术现在被许多实验室使用，并且是几家生物技术公司使用膜和膜蛋白阵列进行筛选的基础。 这一一般研究领域一直是本科生、研究生和博士后研究员的巨大培训来源，经常充当物理科学和生物学之间的桥梁。 在过去的5年里，PI在世界各地的大学、国家实验室、公司和科学会议上进行了100多次受邀演讲。 从广义上看，光合作用研究的概念和结果影响了太阳能研究和新兴的分子电子学领域。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The 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. This research project focuses on three areas: (i) the mechanism of electron transfer in RCs where the primary electron acceptor has been removed; (ii) the use of vibrational spectator probes to quantify electrostatics in the RC; and (iii) the development of advanced imaging techniques using well-defined photosynthetic complexes and assemblies as a model system. By working with RCs in which normal electron transfer is blocked, new pathways can be revealed in a clean background and important intermediates can be trapped. In particular, the kinetics and energetics of electron transfer along the ordinarily non-functional side of the RC can be studied in depth. This project will investigate the orientation of a particular amino acid that is believed to modulate reaction energetics. A suite of methods will introduce spectator vibrational probes into the RC to measure differences in electrostatic fields in symmetry-related positions, as well as probe changes in fields as electron transfer occurs. Areas (i) and (ii) focus on specific, well-defined questions that arise in bacterial photosynthesis; the results and methods will apply to more complex photosynthetic organisms and the broad area of biological electron transfer. Area (iii) uses photosynthetic systems, but will impact the development of new approaches for characterizing membranes and membrane proteins in general. Imaging mass spectrometry will be pushed to its limit using the highly organized photosynthetic membrane, in particular to see whether integral membrane protein organization can be visualized. A "membrane interferometer" has been developed that combines advanced fabrication, membrane assembly and optics in a device that is highly sensitive to membrane curvature and osmotic pressure. Photosynthetic proteins will be used to test the precision of this interferometer, to test hypotheses concerning the impact of photosynthetic membrane proteins on membrane curvature and budding, and as reporters of membrane curvature upon incorporation of channels that are sensitive to membrane tension.Sustained support in this area has led to the development of many new approaches for studying electron transfer reactions, one of the most important classes of reactions in physical and biological systems. 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. Assembly of RCs on surfaces opened an entirely new area of technology, membrane patterning, which is now used in many laboratories and is the basis of efforts to use membrane and membrane-protein arrays for screening in several biotechnology companies. This general area of research has been a tremendous source of training for undergraduates, graduate students and postdoctoral fellows, often serving as a bridge between the physical sciences and biology. The PI has given more than 100 invited talks at universities, national labs, companies and scientific conferences worldwide over the past 5 years. Viewed in broadest terms, concepts and results from photosynthesis research have impacted solar energy research and the emerging area of molecular electronics.