title: Secondary electron transfer in reaction centers of Rhodopseudomonas sphaeroides. Out-of-phase periodicity of two for the formation of ubisemiquinone and fully reduced ubiquinone.
abstract: Electron transfer between purified reaction centers from Rhodopseudomonas sphaeroides and exogenous ubiquinone has been studied in the presence of electron donors by measurements of light-induced absorbance changes following a sequence of short actinic light flashes. Each odd flash promotes the formation of a molecule of ubisemiquinone; after each even flash the semiquinone disappears and a molecule of the fully reduced quinone appears. We interpret these results by means of a model where a specialized molecule of ubiquinone is reduced by the primary electron acceptor in a one-electron transfer reaction after each flash, and is reoxidized by a molecule of the ubiquinone pool in a two-electron transfer reaction every two flashes.
mesh_terms: D003624:Darkness; D004579:Electron Transport; D004735:Energy Transfer; D007700:Kinetics; D008027:Light; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D014451:Ubiquinone