title: The Mössbauer Parameters of the Proximal Cluster of Membrane-Bound Hydrogenase Revisited: A Density Functional Theory Study.
abstract: An unprecedented [4Fe-3S] cluster proximal to the regular [NiFe] active site has recently been found to be responsible for the ability of membrane-bound hydrogenases (MBHs) to oxidize dihydrogen in the presence of ambient levels of oxygen. Starting from proximal cluster models of a recent DFT study on the redox-dependent structural transformation of the [4Fe-3S] cluster, (57)Fe Mössbauer parameters (electric field gradients, isomer shifts, and nuclear hyperfine couplings) were calculated using DFT. Our results revise the previously reported correspondence of Mössbauer signals and iron centers in the [4Fe-3S](3+) reduced-state proximal cluster. Similar conflicting assignments are also resolved for the [4Fe-3S](5+) superoxidized state with particular regard to spin-coupling in the broken-symmetry DFT calculations. Calculated (57)Fe hyperfine coupling (HFC) tensors expose discrepancies in the experimental set of HFC tensors and substantiate the need for additional experimental work on the magnetic properties of the MBH proximal cluster in its reduced and superoxidized redox states.
authors.affiliation: Technical University of Berlin , Institute for Chemistry and Theoretical Chemistry, Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Shadan Ghassemi
authors.initials: SG
authors.lastname: Tabrizi
authors.affiliation: Technical University of Berlin , Institute for Chemistry and Theoretical Chemistry, Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Pelmenschikov
authors.affiliation: Department of Integrative Structural and Computational Biology, The Scripps Research Institute , 10550 North Torrey Pines Road, CB213, La Jolla, California 92037, United States.
authors.forename: Louis
authors.initials: L
authors.lastname: Noodleman
authors.affiliation: Technical University of Berlin , Institute for Chemistry and Theoretical Chemistry, Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kaupp
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D007506:Iron-Sulfur Proteins; D007501:Iron; D006864:Hydrogenase; D010100:Oxygen