Localized Electronic Structure of Nitrogenase FeMoco Revealed by Selenium K-Edge High Resolution X-ray Absorption Spectroscopy
| Autor: | Serena DeBeer, Douglas C. Rees, Dimosthenis Sokaras, Sergey Koroidov, Renee J. Arias, Thomas Kroll, Uwe Bergmann, Justin T. Henthorn |
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| Rok vydání: | 2019 |
| Předmět: |
Models
Molecular Molybdoferredoxin FeMoco Protein Conformation Electrons Electronic structure 010402 general chemistry 01 natural sciences Biochemistry Article Catalysis Selenium chemistry.chemical_compound Colloid and Surface Chemistry Bacterial Proteins Azotobacter vinelandii X-ray absorption spectroscopy biology Extended X-ray absorption fine structure Resolution (electron density) Active site General Chemistry Time-dependent density functional theory 0104 chemical sciences Crystallography X-Ray Absorption Spectroscopy chemistry K-edge biology.protein |
| Zdroj: | Journal of the American Chemical Society |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The size and complexity of Mo-dependent nitrogenase, a multicomponent enzyme capable of reducing dinitrogen to ammonia, have made a detailed understanding of the FeMo cofactor (FeMoco) active site electronic structure an ongoing challenge. Selective substitution of sulfur by selenium in FeMoco affords a unique probe wherein local Fe-Se interactions can be directly interrogated via high-energy resolution fluorescence detected X-ray absorption spectroscopic (HERFD XAS) and extended X-ray absorption fine structure (EXAFS) studies. These studies reveal a significant asymmetry in the electronic distribution of the FeMoco, suggesting a more localized electronic structure picture than is typically assumed for iron-sulfur clusters. Supported by experimental small molecule model data in combination with time dependent density functional theory (TDDFT) calculations, the HERFD XAS data is consistent with an assignment of Fe2/Fe6 as an antiferromagnetically coupled diferric pair. HERFD XAS and EXAFS have also been applied to Se-substituted CO-inhibited MoFe protein, demonstrating the ability of these methods to reveal electronic and structural changes that occur upon substrate binding. These results emphasize the utility of Se HERFD XAS and EXAFS for selectively probing the local electronic and geometric structure of FeMoco. |
| Databáze: | OpenAIRE |
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