title: Ascorbate reacts with singlet oxygen to produce hydrogen peroxide.
abstract: Singlet oxygen is a highly reactive electrophilic species that reacts rapidly with electron-rich moieties, such as the double bonds of lipids, thiols, and ascorbate (AscH-). The reaction of ascorbate with singlet oxygen is rapid (k = 3 x 10(8) M(-1) s(-1)). Here we have investigated the stoichiometry of this reaction. Using electrodes to make simultaneous, real-time measurements of oxygen and hydrogen peroxide concentrations, we have investigated the products of this reaction. We have demonstrated that hydrogen peroxide is a product of this reaction. The stoichiometry for the reactants of the reaction (1 1O2 + 1AscH--->1H2O2 + 1dehydroascorbic) is 1:1. The formation of H2O2 results in a very different oxidant that has a longer lifetime and much greater diffusion distance. Thus, locally produced singlet oxygen with a half-life of 1 ns to 1 micros in a biological setting is changed to an oxidant that has a much longer lifetime and thus can diffuse to distant targets to initiate biological oxidations.
authors.affiliation: Free Radical and Radiation Biology and The University of Iowa, Iowa City, IA, USA.
authors.forename: Galina G
authors.initials: GG
authors.lastname: Kramarenko
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Hummel
authors.forename: Sean M
authors.initials: SM
authors.lastname: Martin
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D017323:Dihematoporphyrin Ether / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D016877:Oxidants; D026082:Singlet Oxygen / Q000737:chemistry*
chemical_list: D016877:Oxidants; D026082:Singlet Oxygen; D017323:Dihematoporphyrin Ether; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid