X-RAY ABSOPTION STUDY ON BACTERIOCHLOROPHYLL ORGANIZATION IN CHLOROSOMES

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。绿色体是来自丝状和硫绿色光合细菌的捕光复合物。叶绿体是自然界中发现的唯一光合天线复合体，其中叶绿素分子不是由蛋白质基质组织的，而是由各种细菌叶绿素（BChl）分子本身之间的相互作用组织的。它也是唯一的天线复杂的结构信息仍然稀缺。引导绿色体自组装的活性位点之一是BChl卟啉环中的中心镁原子。我们的目的是阐明的细节，分子间键合的绿色体探测周围的镁网站与X射线吸收光谱。所需的光子能量范围为1300 eV至2000 eV及以上。我们的计划是比较BChl键合在本地叶绿体一系列的多晶叶绿素样品与已知的结构。此外，我们的模拟表明，镁配位数和键长的氧原子从相邻的BChl分子可以得到从XANES和EXAFS信号。

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. Chlorosomes are light harvesting complexes from filamentous and sulphur green photo-synthetic bacteria. The chlorosome is the only photosynthetic antenna complex found in nature in which the chlorophyll molecules are not organized by a protein matrix, but by interactions between the various bacteriochlorophyll (BChl) molecules themselves. It is also the only antenna complex for which structural information is still scarce. One of the active sites guiding the self-assembly of chlorosomes is the central magnesium atom in the BChl porphyrin ring. We aim to elucidate the details of the inter-molecular bonding in chlorosomes by probing the surroundings of the magnesium site with X-ray absorption spectroscopy. The required photon energies range from 1300 eV to 2000 eV and above. Our plan is to compare the BChl bonding in native chlorosomes to a series of polycrystalline chlorophyll samples with known structures. In addition, our simulations show that Mg-coordination numbers and bond lengths to oxygen atoms from neighboring BChl molecules can be obtained from the XANES and EXAFS signals.