The project focuses on the mechanisms of action of enzymes called hydrogenases, of which there are two, [NiFe]- and the [FeFe]-hydrogenases, reflecting the metals at the active sites. These enzymes, which underpin H2-dependent metabolism of many pathogens in the human gut, act on two substrates protons (H+) and H2. Several related families of enzymes are known. The results are further relevant to fundamental catalyst technology. The work aims to clarify the structure and reactivity of the Ni-C, Ni-SI, Ni-R and Ni-L states of the [NiFe]-hydrogenases and the Hred state of the [FeFe]-hydrogenases. Special attention is directed at the location and behavior H2-derived substrates that are usually invisible to protein spectroscopy and are undetectable by protein crystallography. The active sites of these enzymes are highly unusual, featuring several distinctive cofactors, such as CO, cyanide, and, in the [FeFe] case, an aminodithiolate. The work employs the tools of organometallic chemistry to produce models (replicas) of the active sites. Molecular-level insights into behavior of the hydrogenic ligands will be examined by NMR spectroscopy and X-ray crystallography with attention to stereochemistry, redox potentials, acid-base behavior, and kinetic properties. The first theme examines methods for stabilizing nickelIII, characteristic of N-C state, using organometallic ligands that emulate the donor properties of thiolate ligands. The second theme examines the role of the cyanide cofactors bound to Fe, with attention to developing tools to modify the behavior of these groups.
This aim builds on preliminary evidence that boron reagents enable biomimetic activation of hydrogen in iron cyanides. The third theme, with a primary focus on the [FeFe] enzymes, elucidates the factors that lead to bidirectionality, the ability of models to both produce and oxidized H2. The last theme, which also emphasizes [FeFe]-hydrogenase, examines hypotheses that seek to explain the unusual structure-function of the reduced state of the enzyme. This theme will lead to new ligand scaffolds that stabilize terminal hydride ligands.

Public Health Relevance

Hydrogen is a metabolic substrate and product for both pathogenic and beneficial members of human gut flora. This metabolism is mediated by hydrogenase enzymes. Through the work proposed herein we will elucidate the function of these enzymes on a molecular level, with emphasis on interactions involving iron and hydrogen.

National Institute of Health (NIH)
Research Project (R01)
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Macromolecular Structure and Function A Study Section (MSFA)
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Anderson, Vernon
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University of Illinois Urbana-Champaign
Schools of Arts and Sciences
United States
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Huynh, Mioy T; Wang, Wenguang; Rauchfuss, Thomas B et al. (2014) Computational investigation of [FeFe]-hydrogenase models: characterization of singly and doubly protonated intermediates and mechanistic insights. Inorg Chem 53:10301-11
Huynh, Mioy T; Schilter, David; Hammes-Schiffer, Sharon et al. (2014) Protonation of nickel-iron hydrogenase models proceeds after isomerization at nickel. J Am Chem Soc 136:12385-95
Schilter, David; Pelmenschikov, Vladimir; Wang, Hongxin et al. (2014) Synthesis and vibrational spectroscopy of (57)Fe-labeled models of [NiFe] hydrogenase: first direct observation of a nickel-iron interaction. Chem Commun (Camb) 50:13469-72
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Schilter, David; Nilges, Mark J; Chakrabarti, Mrinmoy et al. (2012) Mixed-valence nickel-iron dithiolate models of the [NiFe]-hydrogenase active site. Inorg Chem 51:2338-48
Pelmenschikov, Vladimir; Guo, Yisong; Wang, Hongxin et al. (2011) Fe-H/D stretching and bending modes in nuclear resonant vibrational, Raman and infrared spectroscopies: comparisons of density functional theory and experiment. Faraday Discuss 148:409-20; discussion 421-41
Barton, Bryan E; Olsen, Matthew T; Rauchfuss, Thomas B (2010) Artificial hydrogenases. Curr Opin Biotechnol 21:292-7
Galinato, Mary Grace I; Whaley, C Matthew; Lehnert, Nicolai (2010) Vibrational analysis of the model complex (mu-edt)[Fe(CO)(3)](2) and comparison to iron-only hydrogenase: the activation scale of hydrogenase model systems. Inorg Chem 49:3201-15
Barton, Bryan E; Rauchfuss, Thomas B (2010) Hydride-Containing Models for the Active Site of the Nickel-Iron Hydrogenases. J Am Chem Soc :
Whaley, C Matthew; Rauchfuss, Thomas B; Wilson, Scott R (2009) Coordination chemistry of [HFe(CN)(2)(CO)(3)](-) and its derivatives: toward a model for the iron subsite of the [NiFe]-hydrogenases. Inorg Chem 48:4462-9

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