[Frontier Leaders] X-ray spectroscopic studies of biological dinitrogen reduction in the Molybdenum and Vanadium Nitrogenases
Serena DeBeer, Max Planck Institute for Chemical Energy Conversion, Germany
| When |
15 May, 2015
from
12:00 pm to 01:00 pm |
|---|---|
| Where | Auditorium |
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Frontier Leaders Seminar
Title: X-ray spectroscopic studies of biological dinitrogen reduction in the Molybdenum and Vanadium Nitrogenases
Speaker: Serena DeBeer
Affiliation: Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany & Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
Abstract:
The conversion of dinitrogen to ammonia is a challenging, energy intensive process, which is enabled biologically by the nitrogenase family of enzymes. By far the most studied nitrogenases are the Mo-dependent forms, which contain a MoFe7S9C cluster, the so-called FeMoco active site, where N2 to NH3 conversion occurs. The presence of a central carbon in this cluster was revealed by a combination of valence-to-core X-ray emission spectroscopy (VtC XES), high-resolution crystallography and pulsed EPR methods. However, numerous questions about the electronic structure of this cluster and how it enables such remarkable reactivity remain. Herein, a brief overview of the recent contributions of X-ray spectroscopy to our understanding of biological nitrogen reduction will be given. This will include highresolution Mo X-ray absorption (XAS) studies, which have revealed the presence of an unusual spin-coupled Mo(III) site in the FeMoco cluster. In addition, Mössbauer and highresolution Fe XAS studies, which have been used to establish the oxidation state distribution of the iron atoms will be presented. Finally, very recent VtC XES and high-resolution Fe XAS studies of the Vanadium-dependent nitrogenases will be presented. While the molybdenum-dependent forms of the enzymes are far better nitrogenases, the vanadiumdependent enzymes have been shown to effectively enable carbon-carbon bond coupling. The differences in the FeMoco and FeVco electronic structures will be discussed, with an emphasis on the potential role of the heterometal in modifying the enzymatic selectivity.
