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).

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 我们建议使用溶液和单晶XAS光谱来研究参与O2结合的两种血红素蛋白。第一个研究将是细胞色素c过氧化物酶，它催化双氧水的两电子还原为水。过氧化氢的还原是通过形成两个高价的血红素中间体：化合物I和化合物II进行的。我们计划使用单晶Fe K边XAS和EXAFS来研究化合物I，以确定光还原的速度和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，以了解这两个高价态在几何结构和电子结构上的差异。XAS数据将与DFT(密度泛函理论)和FeK-Pre-Edge Time DFT计算相耦合，这将有助于揭示CCP催化H_2O_2还原机理中形成的中间产物。在第二个研究中，我们建议使用Fe K-前边分析和含时密度泛函理论相结合的方法来研究氧合血红蛋白的电子结构。这些数据将与脱氧血红蛋白、高铁血红蛋白和血红素模型络合物相关联，以准确区分氧合血红蛋白中存在的[(血红素)Fe-O2]物种的下列可能的电子构型：i)低自旋S=0FeII+单重态S=0O2，ii)中自旋S=1FeII+三重态S=1O2(反铁磁性(AF)耦合)和iii)低自旋S=1/2FeIII+S=1/2O2-(超氧化物)。