Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume 143, Issue 22, Pages 8237-8243Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jacs.1c02323
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Funding
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy [EXC 2008-390540038]
- DFG [SPP 1927, BI 2198/1-1]
- Max Planck Society
- U.S. National Institutes of Health [GM61153]
- NIH [GM65440]
- U.S. Department of Energy Office of Science User Facility [DE-AC02-05CH11231]
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This study used isotopic labeling, Fe-57 nuclear resonance vibrational spectroscopy (NRVS), and density functional theory (DFT) calculations to observe and characterize vibrational modes involving motion of the ligand in [FeFe] hydrogenases. The findings provide insights into the reaction mechanism and dynamics of the hydrogenase enzyme.
[FeFe] hydrogenases are highly active catalysts for the interconversion of molecular hydrogen with protons and electrons. Here, we use a combination of isotopic labeling, Fe-57 nuclear resonance vibrational spectroscopy (NRVS), and density functional theory (DFT) calculations to observe and characterize the vibrational modes involving motion of the 2-azapropane-1,3-dithiolate (ADT) ligand bridging the two iron sites in the [2Fe](H )subcluster. A -(CH2)-C-13-H-2- ADT labeling in the synthetic diiron precursor of [2Fe](H) produced isotope effects observed throughout the NRVS spectrum. The two precursor isotopologues were then used to reconstitute the H-cluster of [FeFe] hydrogenase from Chlamydomonas reinhardtii (CrHydA1), and NRVS was measured on samples poised in the catalytically crucial H-hyd state containing a terminal hydride at the distal Fe site. The (CH)-C-13-H-2 isotope effects were observed also in the H-hyd spectrum. DFT simulations of the spectra allowed identification of the Fe-57 normal modes coupled to the ADT ligand motions. Particularly, a variety of normal modes involve shortening of the distance between the distal Fe-H hydride and ADT N-H bridgehead hydrogen, which may be relevant to the formation of a transition state on the way to H-2 formation.
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