STRUCTURE & FUNCTION OF PHOTOSYNTHETIC REACTION CENTERS

在最广泛的意义上，我们的目标是从物理机制的角度理解生物过程和现象，即在分子水平上。这项提议涉及的主要问题是将电磁能(光)转化为化学能，即光合作用。这个过程是由一个被称为反应中心(RC)的完整的膜蛋白-色素复合体来调节的。我们的工作集中在光合细菌RB的RC的结构方面。球状结构和对区域中心功能的结构影响。在RC中发生的电子和质子转移的机制在所有生命系统中都具有普遍的重要性。例如，在线粒体中发生的过程(在哺乳动物细胞中)可以被视为使用类似机制的光合作用的反向过程。因此，对电子和质子转移机制的了解将有助于更深入地了解某些代谢缺陷的分子基础。这项建议中使用的领域和方法是跨学科的，从物理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射线结晶学、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：来自光合细菌RB的原生和突变RCS的三维结构。Sphaeroides和瞬时RC-cytc2复合体的结构。这些研究由X射线结晶学进行，并辅之以磁共振技术。用动力学光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-AQB-&GT；QAQ-B)和k(2)AB(Q-AQ-B+H+&GT；Q(QBH)-)的质子化反应机理，以及次苯二酚QB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.