title: Electron nuclear double resonance of semiquinones in reaction centers of Rhodopseudomonas sphaeroides.
abstract: Replacement of Fe2+ by Zn2+ in reaction centers of Rhodopseudomonas sphaeroides enabled us to perform ENDOR (electron nuclear double resonance) experiments on the anion radicals of the primary and secondary ubiquinone acceptors (QA- and QB-. Differences between the QA and QB sites, hydrogen bonding to the oxygens, interactions with the protons of the proteins and some symmetry properties of the binding sites were deduced from an analysis of the ENDOR spectra.
authors.forename: W
authors.initials: W
authors.lastname: Lubitz
authors.forename: E C
authors.initials: EC
authors.lastname: Abresch
authors.forename: R J
authors.initials: RJ
authors.lastname: Debus
authors.forename: R A
authors.initials: RA
authors.lastname: Isaacson
authors.forename: M Y
authors.initials: MY
authors.lastname: Okamura
authors.forename: G
authors.initials: G
authors.lastname: Feher
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006860:Hydrogen Bonding; D010084:Oxidation-Reduction; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014451:Ubiquinone