title: Peroxynitrite is the major species formed from different flux ratios of co-generated nitric oxide and superoxide: direct reaction with boronate-based fluorescent probe.
abstract: There is much interest in the nitration and oxidation reaction mechanisms initiated by superoxide radical anion (O(2)()) and nitric oxide ((*)NO). It is well known that O(2) and (*)NO rapidly react to form a potent oxidant, peroxynitrite anion (ONOO(-)). However, indirect measurements with the existing probes (e.g. dihydrorhodamine) previously revealed a bell-shaped response to co-generated (*)NO and O(2) fluxes, with the maximal yield of the oxidation or nitration product occurring at a 1:1 ratio. These results raised doubts on the formation of ONOO(-) per se at various fluxes of (*)NO and O(2). Using a novel fluorogenic probe, coumarin-7-boronic acid, that reacts stoichiometrically and rapidly with ONOO(-) (k = 1.1 x 10(6) m(-1)s(-1)), we report that ONOO(-) formation increased linearly and began to plateau after reaching a 1:1 ratio of co-generated (*)NO and O(2) fluxes. We conclude that ONOO(-) is formed as the primary intermediate during the reaction between (*)NO and O(2) co-generated at different fluxes.
authors.affiliation: Department of Biophysics and Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Jacek
authors.initials: J
authors.lastname: Zielonka
authors.forename: Adam
authors.initials: A
authors.lastname: Sikora
authors.forename: Joy
authors.initials: J
authors.lastname: Joseph
authors.forename: Balaraman
authors.initials: B
authors.lastname: Kalyanaraman
mesh_terms: D001897:Boronic Acids / Q000737:chemistry*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003374:Coumarins / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007093:Imidazoles / Q000737:chemistry; D007700:Kinetics; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013481:Superoxides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001897:Boronic Acids; D003374:Coumarins; D005456:Fluorescent Dyes; D007093:Imidazoles; D016877:Oxidants; C517283:coumarin 7; D013481:Superoxides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D006861:Hydrogen Peroxide