X-RAY SPECTROSCOPY OF PHOTOSYSTEM II SINGLE CRYSTALS

PHOTOSYSTEM II 单晶的 X 射线光谱

• 批准号: 8170189
• 负责人: VITTAL YACHANDRA
• 金额: $ 4.51万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2011-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8170189
• 关键词: Binding Proteins; Biochemical; Charge; Chemistry; Chlorophyll; Complex; Computer Retrieval of Information on Scientific Projects Database; Coupled; Cyanobacterium; Dependence; Electronics; Electrons; Environment; Evolution; Funding; Grant; Institution; Label; Membrane; Methods; Modeling; Mono-S; Nature; Oxygen; Plants; Property; Protein Binding; Reaction; Research; Research Personnel; Resources; Site; Source; Spectrum Analysis; Structure; Techniques; United States National Institutes of Health; Water; dichroism; insight; oxidation; photosystem; photosystem II; protein complex; research study; synchrotron radiation; vector

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Photosystem II (PS II) is a membrane-bound protein complex found in green plants and cyanobacteria, which catalyzes photosynthetic water oxidation and oxygen evolution. Single-electron photo-oxidations of a specialized chlorophyll molecule in the reaction center are coupled to the four-electron oxidation of water by the oxygen-evolving complex (OEC) in PS II through five intermediate states labeled S0-S4. A protein-bound complex of four Mn atoms is thought to be the site of water oxidation chemistry and to function in charge accumulation. Although this Mn complex has been the subject of numerous biochemical and spectroscopic studies, the exact structure of the complex and the mechanism of water oxidation remain unknown. Although x-ray spectroscopic methods have been perhaps the most informative technique used to derive detailed information about the oxidation states of and the environment surrounding Mn in the OEC most of the x-ray spectroscopic studies were performed on randomly oriented PS II membranes; thus, no angle dependence of EXAFS features was observed. The ability to exploit the plane-polarized nature of synchrotron radiation has made possible the study of dichroism in oriented PS II membranes, mostly, in terms of the orientation dependence of the Mn?Mn vectors in the di-u-oxo and mono-u-oxo bridged Mn2 motifs that have been shown to be present in the OEC. In this proposal we describe experiments with single crystals of Mn model compounds and photosystem II. We expect the present study will provide important insights to the structure of the Mn complex and its electronic properties that are critical for understanding the mechanism of water oxidation and oxygen evolution.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目及 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 光系统 II (PS II) 是一种在绿色植物和蓝细菌中发现的膜结合蛋白复合物，可催化光合水氧化和氧气释放。反应中心中特定叶绿素分子的单电子光氧化通过 PS II 中的析氧络合物 (OEC) 通过标记为 S0-S4 的五个中间态与水的四电子氧化耦合。四个锰原子的蛋白质结合复合物被认为是水氧化化学的场所并在电荷积累中发挥作用。尽管这种锰络合物已成为众多生化和光谱研究的主题，但该络合物的确切结构和水氧化机制仍然未知。尽管 X 射线光谱方法可能是用于获取有关 OEC 中 Mn 的氧化态及其周围环境的详细信息的信息最丰富的技术，但大多数 X 射线光谱研究都是在随机取向的 PS II 膜上进行的；因此，没有观察到 EXAFS 特征的角度依赖性。利用同步加速器辐射的平面偏振性质的能力使得定向 PS II 膜中的二色性研究成为可能，主要是根据二-u-氧和单-u 中 Mn?Mn 矢量的方向依赖性。 -oxo 桥接 Mn2 基序已被证明存在于 OEC 中。在本提案中，我们描述了 Mn 模型化合物单晶和光系统 II 的实验。我们期望本研究将为锰配合物的结构及其电子特性提供重要的见解，这对于理解水氧化和氧气析出的机制至关重要。