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).

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