Synthetic Models of the Oxygen Evolving Complex of Photosystem II

光系统II放氧复合物的合成模型

• 批准号: 9278192
• 负责人: Theodor Agapie
• 金额: $ 28.55万
• 依托单位: CALIFORNIA INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2018-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9278192
• 关键词: Active Sites; Address; Behavior; Benchmarking; Biochemical; Biochemical Reaction; Biological; Biological Models; Biological Process; Catalysis; Cations; Chemicals; Chemistry; Complement; Complex; Cyanobacterium; Data; Dioxygen; Electron Transport; Electrons; Family; Generations; Goals; Hand; Heme; Human; Investigation; Ions; Ligands; Metals; Mission; Modeling; Nature; Organism; Oxidation-Reduction; Oxygen; Photosynthesis; Plants; Process; Production; Property; Proteins; Protons; Reaction; Role; Route; Site; Structural Models; Structure; System; Testing; Theoretical Studies; United States National Institutes of Health; Water; Work; X ray spectroscopy; alkalinity; biological systems; chemical property; interest; manganese oxide; metal complex; metal oxide; oxidation; photosystem II; physical property; protein complex; protonation; public health relevance; small molecule

DESCRIPTION (provided by applicant): Biological dioxygen generation occurs within Photosystem II (PSII) in cyanobacteria and plants. The active site responsible for this transformation, the Oxygen Evolving Complex (OEC), consists of a Mn4CaOn cluster embedded in a large protein complex. Given the broad fundamental interest and potential applications of water splitting to make dioxygen, the structure of this cluster and the mechanism of catalysis have been the subject of many spectroscopic, computational, synthetic, crystallographic and biochemical studies. Despite significant advances, the mechanism of oxygen production is still not well understood. The exact Mn oxidation states along the catalytic cycle and the site of O-O bond formation continue to be debated. The large protein matrix has complicated direct studies of the OEC active site and the synthesis of accurate small-molecule models has been hampered by the complexity of the cluster. Our goals include developing synthetic routes to MnxMOn models (x=3, 4; M=Ca, Mn, other metals) of the OEC and undertaking mechanistic studies that will allow a deeper understanding of the effects different constituents (metals, ancillary and oxo ligands, protonation state) have on the chemical and physical properties of the cluster relevant to achieving high oxidation states and effecting O2 production. To that end, we will test hypotheses regarding electron, oxygen-atom and proton transfers and ligand substitution in these complex systems with implications for the assembly of the clusters and O-O bond formation. With few exceptions, the synthesis of predictable manganese oxide clusters has been frustrated by the propensity of oxo ligands to bridge and form complicated oligomeric structures. Our approach to overcoming this problem is to use relatively small, but rigid organic frameworks to support trimanganese complexes that have been elaborated to site-differentiated metal-oxo clusters, including a Mn3CaO4 moiety. These structural models will allow for spectroscopic benchmarking (EPR, XES, XAS) in comparison with the biological system. Our work on synthetic complexes will complement the studies performed on the protein by allowing systematic structure- reactivity studies to uncover the chemical features that control the properties of these clusters and the mechanism of catalysis.

描述（由申请人提供）：生物二氧化物产生发生在蓝细菌和植物中的光系统II（PSII）内。负责这种转化的活性位点，氧气演变的复合物（OEC）由嵌入大蛋白质复合物中的MN4CAON簇组成。鉴于水分分裂以制造二恶英的广泛基本兴趣和潜在应用，该群集的结构和催化机理一直是许多光谱，计算，合成，晶体学和生化研究的主题。尽管取得了重大进展，但氧气产生的机制仍然不太了解。沿催化循环和O-O键形成的位点的确切MN氧化态继续进行辩论。大型蛋白质基质对OEC活性位点进行了复杂的直接研究，并且精确的小分子模型的合成受到了群集的复杂性的阻碍。我们的目标包括为MNXMON模型开发合成途径（X = 3，4; M = Ca，Mn，Mn，其他金属）以及进行机械性研究，以使对不同组成型的影响（金属，辅助和氧配体，质子化状态，质子化状态）具有更深入的了解对群集的化学和物理性能的高度氧化和实现高氧化的良好性能。为此，我们将在这些复杂系统中测试有关电子，氧原子和质子转移和配体取代的假设，对簇和O-O键形成的组装有影响。除少数例外，可预测的氧化锰簇的合成被氧配体易于桥接和形成复杂的寡聚结构的倾向而感到沮丧。我们克服这个问题的方法是使用相对较小但刚性的有机框架来支持已详细介绍到现场分化的金属氧簇（包括MN3CAO4部分）的三卫生复合物。与生物系统相比，这些结构模型将允许光谱基准测试（EPR，XES，XAS）。我们在合成复合物上的工作将补充对蛋白质进行的研究，通过允许系统的结构反应性研究来揭示控制这些簇的性质和催化机制的化学特征。