Infrared Spectroscopic Studies of the Photosynthetic Oxygen-Evolving Complex

红外光谱技术将用于研究光合出氧复合体光系统II的结构和功能之间的关系。这些实验将集中在含锰催化位点和33 kDa的锰稳定外源蛋白上。水的氧化是一个四电子反应。光系统II反应中心的含锰催化位点积累了这四个氧化等价物，并通过一系列的五个“S态”循环。振动光谱学将用于获得有关光氧化时锰簇和反应中心发生的结构变化的信息。红外光谱还将用于研究33 kDa蛋白的结构和功能作用。该提案有三个目标：A)使用差分红外光谱来测量和识别光系统II锰团簇氧化时发生的结构变化；B)验证当该外来亚基与光系统II反应中心结合时，33 kDa蛋白发生二级结构变化的假设；C)使用差分红外光谱来确定去除33 kDa蛋白质是否会影响伴随锰团簇氧化的结构变化。植物的光合作用包括将光能转化为化学能。这一过程是通过膜相关蛋白中电子的多步转移来实现的。通过这种电子的转移，在膜上建立了相对稳定的电荷分离。这种电荷分离是由光能驱动的能量存储事件。电子的最终供体是水；从水中除去电子的过程导致氧的释放。这种氧气的产生对维持地球上人类的生命至关重要。该提案将资助对负责氧气产生的膜相关蛋白的研究。产生氧气的化学反应发生在一个由四个锰原子组成的簇上。通过使用振动光谱学，我们将获得关于锰簇的结构和结合位点的新信息，以及关于发生在该金属簇上的化学反应。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. ***