title: A strenuous experimental journey searching for spectroscopic evidence of a bridging nickel-iron-hydride in [NiFe] hydrogenase.
abstract: Direct spectroscopic evidence for a hydride bridge in the Ni-R form of [NiFe] hydrogenase has been obtained using iron-specific nuclear resonance vibrational spectroscopy (NRVS). The Ni-H-Fe wag mode at 675 cm(-1) is the first spectroscopic evidence for a bridging hydride in Ni-R as well as the first iron-hydride-related NRVS feature observed for a biological system. Although density function theory (DFT) calculation assisted the determination of the Ni-R structure, it did not predict the Ni-H-Fe wag mode at ∼ 675 cm(-1) before NRVS. Instead, the observed Ni-H-Fe mode provided a critical reference for the DFT calculations. While the overall science about Ni-R is presented and discussed elsewhere, this article focuses on the long and strenuous experimental journey to search for and experimentally identify the Ni-H-Fe wag mode in a Ni-R sample. As a methodology, the results presented here will go beyond Ni-R and hydrogenase research and will also be of interest to other scientists who use synchrotron radiation for measuring dilute samples or weak spectroscopic features.
authors.affiliation: Department of Chemistry, University of California, 1 Cyclotron Road, Davis, CA 95616, USA.
authors.forename: Hongxin
authors.initials: H
authors.lastname: Wang
authors.affiliation: Research and Utilization Division, SPring-8/JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yoda
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ogata
authors.affiliation: Research and Utilization Division, SPring-8/JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D004789:Enzyme Activation; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D006864:Hydrogenase / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D011485:Protein Binding
chemical_list: D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase
keywords: NRVS; Ni–H–Fe wag mode; Ni–R; [NiFe] hydrogenase; iron hydride; nuclear resonance vibrational spectroscopy; ultra-weak signal