title: Effects of oxygen on the dark recombination between photoreduced secondary quinone and oxidized bacteriochlorophyll in Rhodobacter sphaeroides reaction centers.
abstract: The influence of duration of exposure to actinic light (from 1 sec to 10 min) and temperature (from 3 to 35 degrees C) on the temporary stabilization of the photomobilized electron in the secondary quinone acceptor (QB) locus of Rhodobacter sphaeroides reaction centers (RC) was studied under aerobic or anaerobic conditions. Optical spectrophotometry and ESR methods were used. The stabilization time increased significantly upon increasing the exposure duration under aerobic conditions. The stabilization time decreased under anaerobic conditions, its dependence on light exposure duration being significantly less pronounced. Generation of superoxide radical in photoactivated aerobic samples was revealed by the ESR method. Possible interpretation of the effects is suggested in terms of interaction between the semiquinone QB with oxygen, the interaction efficiency being determined by the conformational transitions in the structure of RC triggered by actinic light on and off.
authors.affiliation: School of Biology, Lomonosov Moscow State University, Moscow, 119899 Russia. knox@biophys.msu.ru
authors.forename: P P
authors.initials: PP
authors.lastname: Knox
authors.forename: E P
authors.initials: EP
authors.lastname: Lukashev
authors.forename: K N
authors.initials: KN
authors.lastname: Timofeev
authors.forename: N K
authors.initials: NK
authors.lastname: Seifullina
mesh_terms: D000465:Algorithms; D001429:Bacteriochlorophylls / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011809:Quinones; D010100:Oxygen