X-RAY EMISSON SPECTROSCOPY OF THE PHOTOSYNTHETIC MN4CA COMPLEX

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 氧气，支持所有的有氧生命，在大气中是丰富的，因为它不断再生的光合作用水氧化的绿色植物，藻类和蓝藻。该光反应由与光系统II（PS II）相关的Mn 4Ca簇催化。考虑到PS II在维持生物圈生命和可再生能源经济未来愿景中的作用，阐明Mn 4Ca催化剂的结构和机制至关重要，Mn 4Ca催化剂有时被称为？心脏？水的氧化过程。虽然，Mn 4Ca水裂解催化剂的电子和几何结构已被广泛研究，该催化剂的精确结构和机制迄今为止还没有通过X射线衍射（XRD），扩展X射线吸收精细结构（EXAFS）和其他光谱技术的测定的所有尝试。发展高分辨率吸收和发射X射线光谱学的新方法，包括X射线拉曼光谱学、范围扩展EXAFS和位点选择性X射线光谱学，对于提供重要的新信息至关重要，这将有助于阐明不仅是复合物的结构，而且是光合作用水氧化过程的机制。本提案建立在过去的实验基础上，并提出了X射线发射光谱在PS II中Mn络合物的一些新应用，如下所示：a）X射线拉曼或RIXS光谱法，其将解决Mn络合物的电子结构，B）K β发射和位点选择性光谱法，其将选择性地探测Mn络合物中的不同Mn位点或不同氧化态，c）EXAFS的高分辨率Mn K α检测，其将允许我们收集超过Fe K边缘的EXAFS，从而提高分辨率，和d）原子间Mn K β 2，5光谱，其将是Mn的配体原子的探针，特别是用于确定氯化物是否是PS II中Mn的配体。

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. Oxygen, that supports all aerobic life, is abundant in the atmosphere because of its constant regeneration by photosynthetic water oxidation by green plants, algae and cyanobacteria. This light-requiring reaction is catalyzed by a Mn4Ca cluster associated with photosystem II (PS II). Given the role of PS II in maintaining life on the biosphere and the future visions of a renewable energy economy, it is vital to elucidate the structure and mechanism of the Mn4Ca catalyst, which is sometimes referred to as the ?heart? of the water oxidation process. Although, the electronic and geometric structure of the Mn4Ca water-splitting catalyst has been extensively investigated, the precise structure and mechanism of this catalyst has so far eluded all attempts of determination by x-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS) and other spectroscopic techniques. The development of new methods of high resolution absorption and emission x-ray spectroscopy, including x-ray Raman spectroscopy, range-extended EXAFS and site-selective X-ray spectroscopy are critical for providing important new information, that will help in elucidating not only the structure of the complex, but also the mechanism of the photosynthetic water oxidation process. The present proposal builds on the past experiments and addresses some new applications of x-ray emission spectroscopy to the Mn complex in PS II as follows: a) X-ray Raman or RIXS spectroscopy that will address the electronic structure of the Mn complex, b) Kbeta emission and site selective spectroscopy that will selectively probe different Mn sites or different oxidation states in the Mn complex, c) High resolution Mn Kalpha detection of EXAFS that will allow us to collect EXAFS beyond the Fe K-edge thus improving resolution and d) Interatomic Mn Kbeta2,5 spectra that will be a probe for the ligand atoms of Mn, especially to ascertain whether chloride is a ligand of Mn in PS II.