title: Spin trapping study on the kinetics of Fe2+ autoxidation: formation of spin adducts and their destruction by superoxide.
abstract: The oxidation of Fe2+ was investigated by electron spin resonance spin trapping techniques with N-t-butyl-alpha-phenylnitrone (PBN) and dimethyl sulfoxide. Under pure oxygen, the spin adduct PBN/.OCH3 was rapidly generated by the addition of Fe2+ (0.2-1.2 mM) into phosphate buffer containing ethylenediaminetetraacetate (EDTA), dimethyl sulfoxide, and PBN at pH 7.4, but it decayed. The decay process of PBN/.OCH3 consists of two components. The fast decay was dependent on Fe2+ concentration. Another was due to destruction of the spin adduct by superoxide anion (.O2-), because superoxide dismutase (SOD) markedly prevented the decay. Catalase decreased the yield of PBN/.OCH3. When EDTA was replaced by diethylenetriaminepentaacetic acid (DTPA), both the generation and decay process of PBN/.OCH3 were slow. SOD and catalase effects were similar to those in EDTA. Fe2+ produced PBN/.OCH3 even in the absence of chelators. We could estimate the kinetic parameters by computer simulation, comparing the Fe2+ oxidation in EDTA with that in DTPA. These results demonstrate that Fe2+ reacts with O2 to generate .O2- and then H2O2, which produces .CH3 by reaction with Fe2+ and dimethyl sulfoxide.(.)OCH3 results from the reaction between .CH3 and O2. The adduct PBN/.OCH3 decays by reaction with Fe2+ and .O2-.
authors.affiliation: Department of Physiology, Medical School, Osaka University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kosaka
authors.forename: Y
authors.initials: Y
authors.lastname: Katsuki
authors.forename: T
authors.initials: T
authors.lastname: Shiga
mesh_terms: D000388:Air; D003497:Cyclic N-Oxides; D004492:Edetic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005296:Ferrous Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide; D007501:Iron; D007700:Kinetics; D008958:Models, Molecular; D009589:Nitrogen Oxides / Q000737:chemistry*; D010100:Oxygen / Q000378:metabolism; D004369:Pentetic Acid / Q000737:chemistry*; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000737:chemistry; D013481:Superoxides / Q000494:pharmacology*
chemical_list: D003497:Cyclic N-Oxides; C045076:Fenton's reagent; D005296:Ferrous Compounds; D009589:Nitrogen Oxides; D013113:Spin Labels; D013481:Superoxides; C055526:Fe(II)-EDTA; C029217:phenyl-N-tert-butylnitrone; D004369:Pentetic Acid; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D013482:Superoxide Dismutase; D010100:Oxygen