SINGLE CRYSTAL XAS STUDIES ON O2 ACTIVATING HEME PROTEINS

O2 激活血红素蛋白的单晶 XAS 研究

• 批准号: 8362248
• 负责人: BRITT HEDMAN
• 金额: $ 2.19万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2012-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8362248
• 关键词: Binding; Complex; Coupled; Cytochrome c Peroxidase; Data; Electronics; Electrons; Funding; Grant; Heme; Hemeproteins; Hydrogen Peroxide; Light; Methemoglobin; Modeling; National Center for Research Resources; Oxyhemoglobin; Principal Investigator; Radiation; Research; Research Infrastructure; Resources; Signal Transduction; Solutions; Source; Spectrum Analysis; Superoxides; Sushi Domain; Time; Triplet Multiple Birth; United States National Institutes of Health; Water; cost; density; deoxyhemoglobin; electronic structure; structural biology; theories

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We propose to investigate two heme proteins involved in O2 binding using solution and single crystal XAS spectroscopy. The first study will be on cytochrome c peroxidase, which catalyzes the two-electron reduction of H2O2 to water. The reduction of H2O2 proceeds via the formation of two high-valent heme intermediates; compound I and compound II. We plan to study compound I using single crystal Fe K-edge XAS and EXAFS to determine the rate of photoreduction and the concomitant change in the EXAFS signal (specifically the Fe-O bond). These studies will be extended to compound II of CCP to understand differences in the geometric and electronic structure between the two high-valent states. The XAS data will be coupled to DFT (density functional theory) and Fe K-pre-edge time dependent-DFT calculations, which will help shed light on the intermediates formed in the catalytic mechanism of H2O2 reduction by CCP. In the second study we propose to investigate the electronic structure of oxyhemoglobin using a combination of Fe K-pre-edge analysis and time-dependent DFT calculations. The data will be correlated to deoxyhemoglobin, methemoglobin and heme model complexes to accurately distinguish between the following possible electronic configurations of the [(heme)Fe-O2] species present in oxyhemoglobin: i) low-spin S=0 FeII + singlet S=0 O2, ii) an intermediate-spin S=1 FeII + triplet S=1 O2 (antiferromagnetically (AF) coupled) and iii) a lowspin S=1/2 FeIII + S=1/2 O2 - (superoxide).

该子项目是利用资源的众多研究子项目之一 由 NIH/NCRR 资助的中心拨款提供。子项目的主要支持 并且子项目的主要研究者可能是由其他来源提供的， 包括其他 NIH 来源。 子项目可能列出的总成本 代表子项目使用的中心基础设施的估计数量， NCRR 赠款不直接向子项目或子项目工作人员提供资金。 我们建议使用溶液和单晶 XAS 光谱研究参与 O2 结合的两种血红素蛋白。第一项研究将针对细胞色素 c 过氧化物酶，该酶催化 H2O2 双电子还原为水。 H2O2 的还原是通过形成两种高价血红素中间体进行的；化合物I和化合物II。我们计划使用单晶 Fe K 边 XAS 和 EXAFS 研究化合物 I，以确定光还原速率以及 EXAFS 信号（特别是 Fe-O 键）的伴随变化。这些研究将扩展到 CCP 的化合物 II，以了解两种高价态之间几何和电子结构的差异。 XAS 数据将与 DFT（密度泛函理论）和 Fe K 前边缘时间相关 DFT 计算相结合，这将有助于阐明 CCP 还原 H2O2 催化机制中形成的中间体。在第二项研究中，我们建议结合使用 Fe K 前边缘分析和时间相关的 DFT 计算来研究氧合血红蛋白的电子结构。数据将与脱氧血红蛋白、高铁血红蛋白和血红素模型复合物相关联，以准确区分氧合血红蛋白中存在的 [(heme)Fe-O2] 物质的以下可能的电子构型： i) 低自旋 S=0 FeII + 单线态 S= 0 O2，ii) 中间自旋 S=1 FeII + 三重态 S=1 O2（反铁磁 (AF) 耦合）和 iii) 低自旋S=1/2 FeIII + S=1/2 O2 -（超氧化物）。