Infrared Spectroscopic Studies of the Photosynthetic Oxygen-Evolving Complex

9418164 Barry红外光谱技术将用于研究光合放氧复合体-光系统II的结构和功能之间的关系。这些实验将集中在含锰催化部位和33 kDa稳定锰的外源蛋白上。水的氧化是一个四电子事件。光系统II反应中心的含锰催化中心积累了这四种氧化当量，并通过一系列的五种“S态”循环。振动光谱将被用来获得关于光氧化时在锰团簇和反应中心发生的结构变化的信息。红外光谱也将被用来研究33 kDa蛋白的结构和功能。该建议有三个目标：A)使用差异红外光谱来测量和识别光系统II锰簇氧化时发生的结构变化；B)检验当33 kDa蛋白质的外在亚基与光系统II反应中心结合时发生二级结构变化的假设；C)使用差异红外光谱来确定去除33 kDa蛋白质是否影响伴随着锰簇氧化的结构变化。植物的光合作用涉及将光能转化为化学能。这一过程是通过膜结合蛋白中电子的多步转移进行的。通过这种电子转移，在整个膜上建立了一个相对稳定的电荷分离。这种电荷分离是能量储存事件，由光能驱动。电子的最终给体是水；从水中去除电子的过程导致氧的释放。这种氧气生产对维持地球上的人类生命至关重要。这项提案将资助对膜相关蛋白的研究，这种蛋白负责产生氧气。制氧化学发生在由四个锰原子组成的团簇中。通过振动光谱的使用，我们将获得有关锰原子簇的结构和结合位置的新信息，以及发生在这个金属原子簇上的化学信息。振动光谱学是研究这些过程的理想技术，因为它对微小的结构变化非常敏感。***

9418164 Barry The technique of infrared spectroscopy will be used to investigate the relationship between structure and function in the photosynthetic oxygen-evolving complex, photosystem II. These experiments will focus on the manganese-containing catalytic site and on the 33 kDa manganese-stabilizing extrinsic protein. The oxidation of water is a four electron event. The manganese- containing catalytic site of the photosystem II reaction center accumulates these four oxidizing equivalents and cycles through a series of five "S states." Vibrational spectroscopy will be used to obtain information concerning the structural changes that occur in the manganese cluster and in the reaction center upon photooxidation. Infrared spectroscopy will also be employed in order to investigate the structure and functional role of the 33 kDa protein. This proposal has three objectives: A) to use difference infrared spectroscopy to measure and to identify the structural changes that occur upon oxidation of the photosystem II manganese cluster; B) to test the hypothesis that secondary structure changes occur in the 33 kDa protein when this extrinsic subunits binds to the photosystem II reaction center; C) to use difference infrared spectroscopy to determine if removal of the 33 kDa protein influences the structural changes that accompany oxidation of the manganese cluster. %%% Photosynthesis in plants involves the conversion of light energy into chemical energy. This process is carried out be the multi- step transfer of electrons in membrane associated proteins. Through this transfer of electrons, a relatively stable separation of charge is built up across the membrane. This charge separation is the energy storage event and is driven by the energy of light. The ultimate donor of electrons is water; the process of removal of electrons from water results in the liberation of oxygen. This oxygen production is critical for the maintenance of human life on earth. This propo sal will fund studies of the membrane associated protein that is responsible for the production of oxygen. Oxygen producing chemistry occurs at a cluster of four manganese atoms. Through the use of vibrational spectroscopy, we will obtain new information concerning the structure and binding site of the manganese cluster, as well as concerning the chemistry that occurs at this metal cluster. Vibrational spectroscopy is the ideal technique to use to investigate these processes, since it is exquisitely sensitive to small structural alterations. ***