title: Environmentally persistent free radicals (EPFRs). 1. Generation of reactive oxygen species in aqueous solutions.
abstract: Reactive oxygen species (ROS) generated by environmentally persistent free radicals (EPFRs) of 2-monochlorophenol, associated with CuO/silica particles, were detected using the chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Yields of hydroxyl radical ((•)OH), superoxide anion radical (O(2)(•-)), and hydrogen peroxide (H(2)O(2)) generated by EPFR-particle systems were reported. Failure to trap superoxide radicals in aqueous solvent, formed from reaction of EPFRs with molecular oxygen, results from fast transformation of the superoxide to hydrogen peroxide. However, formation of superoxide as an intermediate product in hydroxyl radical formation in aprotic solutions of dimethyl sulfoxide (DMSO) and acetonitrile (AcN) was observed. Experiments with superoxide dismutase (SOD) and catalase (CAT) confirmed formation of superoxide and hydrogen peroxide, respectively, in the presence of EPFRs. The large number of hydroxyl radicals formed per EPFR and monotonic increase of the DMPO-OH spin adduct concentration with incubation time suggest a catalytic cycle of ROS formation.
authors.affiliation: Department of Chemistry and LSU Superfund Research Center,  Louisiana State University , Baton Rouge, Louisiana 70803, United States.
authors.forename: Lavrent
authors.initials: L
authors.lastname: Khachatryan
authors.forename: Eric
authors.initials: E
authors.lastname: Vejerano
authors.forename: Slawo
authors.initials: S
authors.lastname: Lomnicki
authors.forename: Barry
authors.initials: B
authors.lastname: Dellinger
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D002417:Cattle; D002733:Chlorophenols / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004785:Environmental Pollutants / Q000138:chemical synthesis*; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000138:chemical synthesis*; D012996:Solutions; D012997:Solvents; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D002733:Chlorophenols; D003497:Cyclic N-Oxides; D004785:Environmental Pollutants; C045076:Fenton's reagent; D017382:Reactive Oxygen Species; D012996:Solutions; D012997:Solvents; D014867:Water; D013481:Superoxides; D017665:Hydroxyl Radical; C069977:2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy; D006861:Hydrogen Peroxide; D007501:Iron; D002374:Catalase; D013482:Superoxide Dismutase; C030683:2-chlorophenol