STRUCTURE & FUNCTION OF PHOTOSYNTHETIC REACTION CENTERS

在最广泛的意义上，我们的目标是了解生物过程和现象的物理机制，即在分子水平上。该提案中解决的主要问题涉及电磁能（光）转化为化学能，即光合作用。这一过程是由一个完整的膜蛋白-色素复合物称为反应中心（RC）介导的。我们的工作重点是从光合细菌Rb的RC的结构方面。sphaeroides和结构上的RC功能的影响。在RC中发生的电子和质子转移的机制在所有生命系统中具有普遍的重要性。例如，在线粒体（哺乳动物细胞）中发生的过程可以被视为利用类似机制的光合作用的逆过程。因此，对电子和质子转移机制的理解应该导致对某些代谢缺陷的分子基础的更深入的理解。该提案中使用的领域和方法是跨学科的，从物理学到化学和分子生物学。因此，在我们的工作中使用了不同的技术和工具，例如计算方法，X射线晶体学，光谱学，磁共振（EPR，ENDOR），蛋白质化学和重组DNA技术。解决的具体问题是：从光合细菌Rb的天然和突变体RC的三维结构。sphaeroides和瞬时RC-cyt c2复合物的结构。这些研究正在进行的X射线晶体学，辅以磁共振技术。目前，利用动力学光谱和定点突变技术研究了两个电子转移反应：k（1）AB（Q-AQ B->QAQ-B）和k（2）AB（Q-AQ-B+H+->Q（QBH）-）的机理，以及仲醌Q B的质子化反应。

In the broadest sense, our objective is to understand biological processes and phenomena in terms of physical mechanisms, i.e. on a molecular level. The main problem addressed in this proposal deals with the conversion of electromagnetic energy (light) into chemical energy, i.e. photosynthesis. This process is mediated by an integral membrane protein - pigment complex called the reaction center (RC). Our work focuses on the structural aspects of the RC from the photosynthetic bacterium Rb. sphaeroides and the structural implications on the function of the RC. The mechanisms of electron and proton transfers that take place in the RC are of general importance in all living systems. For instance, the processes that take place in mitochondria (in mammalian cells) can be viewed as the reverse process of photosynthesis utilizing similar mechanisms. Thus, the understanding of electron and proton transfer mechanisms should lead to a deeper understanding of the molecular basis of some metabolic deficiencies. The fields and methodologies used in this proposal are interdisciplinary, ranging from physics to chemistry and molecular biology. Consequently, different techniques and tools are used in our work, e.g. computational methods, X-ray crystallography, optical spectroscopy, magnetic resonance (EPR, ENDOR), protein chemistry and recombinant DNA techniques. The specific problems addressed are: The three-dimensional structure of native and mutant RCs from the photosynthetic bacterium Rb. sphaeroides and the structure of the transient RC-cyt c2 complex. These studies are being pursued by X-ray crystallography, complemented by magnetic resonance techniques. The mechanisms of two electron transfer reactions: k(1)AB(Q-AQB->QAQ-B) and k(2)AB (Q-AQ-B+H+->Q(QBH)-), as well as the protonation of the secondary quinone, QB, are being studied by kinetic optical spectroscopy and site-directed mutagenesis.