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: 9980923
• 负责人: Theodor Agapie
• 金额: $ 20.94万
• 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 2023-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9980923
• 关键词: Active Sites; Address; Affect; Atmosphere; Behavior; Benchmarking; Binding; Biochemical; Biochemical Reaction; Biological; Biological Models; Biological Process; Catalysis; Chemicals; Complement; Complex; Cyanobacterium; Dioxygen; Electron Spin Resonance Spectroscopy; Electrons; Generations; Goals; Hand; Human; Investigation; Isotope Labeling; Life; Ligands; Metals; Methods; Mission; Modeling; Nature; Organism; Oxidation-Reduction; Oxygen; Photosynthesis; Physiologic pulse; Planet Earth; Plants; Process; Production; Property; Proteins; Protons; Role; Route; Site; Spectrum Analysis; Structural Models; Structure; System; Techniques; Testing; Theoretical Studies; United States National Institutes of Health; Water; Work; X ray spectroscopy; biological systems; chemical property; electronic structure; experimental study; interest; manganese oxide; metal complex; metal oxide; oxidation; photosystem II; physical property; protein complex; protonation; small molecule; spectroscopic survey

Abstract 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. This metal cluster is responsible for the oxygenic atmosphere on Earth, and consequently for most life as we know it. 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 rational synthesis of accurate small- molecule models suitable for structure-function studies 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 its subsites 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 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 close structural and functional models of the biological system. These synthetic clusters 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-property studies to uncover the chemical features that control the reactivity and spectroscopy of these clusters and the mechanism of catalysis.

抽象的 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。这 负责这种转化的主动部位，氧气不断发展的复合物（OEC）由A组成 MN4CAON簇嵌入大型蛋白质复合物中。这个金属簇负责 如我们所知，地球上的氧气气氛，因此在大多数生活中。鉴于广泛 基本的兴趣和水分割的潜在应用以制造二恶英， 该集群和催化的机制已成为许多光谱学的主题 计算，合成，晶体学和生化研究。尽管取得了重大进展，但 氧气产生的机理仍然不太了解。确切的Mn氧化状态沿 催化循环和O-O键形成部位继续进行辩论。大蛋白质基质 对OEC活性位点的直接研究复杂，并且合理合成精确的小型 - 适用于结构功能研究的分子模型受到了复杂性的困扰 簇。 我们的目标包括开发到MNXMON模型的合成路线（x = 3，4; m = ca，mn，其他金属） OEC及其子站点以及进行机械研究，可以更深入地理解 在不同的成分（金属，辅助和氧配体，质子化状态）的影响中， 簇的化学和物理特性与实现高氧化态和 影响O2的产生。为此，我们将检验有关电子，氧原子和 质子转移和配体在这些复杂系统中具有对O-O键的影响 形成。除少数例外，可预测的氧化锰簇的合成已经 因氧配体的倾向而感到沮丧，形成复杂的寡聚结构。我们的 克服这个问题的方法是使用相对较小但僵化的有机框架来支持 详细阐述的三横向群综合体，包括 密闭生物系统的结构和功能模型。这些合成集群将允许 与生物系统相比，光谱基准测试（EPR，XES，XAS）。我们的工作 合成复合物将通过允许系统的 结构性研究，以发现控制反应性和的化学特征 这些簇的光谱和催化机理。