title: Dosimetry determines the initial OH radical concentration in fast photochemical oxidation of proteins (FPOP).
abstract: Fast photochemical oxidation of proteins (FPOP) employs laser photolysis of hydrogen peroxide to give OH radicals that label amino acid side-chains of proteins on the microsecond time scale. A method for quantitation of hydroxyl radicals after laser photolysis is of importance to FPOP because it establishes a means to adjust the yield of •OH, offers the opportunity of tunable modifications, and provides a basis for kinetic measurements. The initial concentration of OH radicals has yet to be measured experimentally. We report here an approach using isotope dilution gas chromatography/mass spectrometry (GC/MS) to determine quantitatively the initial •OH concentration (we found ~0.95 mM from 15 mM H2O2) from laser photolysis and to investigate the quenching efficiencies for various •OH scavengers.
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, MO, 63130-4899, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Niu
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Daryl
authors.initials: D
authors.lastname: Giblin
authors.forename: Don L
authors.initials: DL
authors.lastname: Rempel
authors.forename: Michael L
authors.initials: ML
authors.lastname: Gross
mesh_terms: D003903:Deuterium; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D005973:Glutamine / Q000737:chemistry / Q000494:pharmacology; D006639:Histidine / Q000737:chemistry / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000032:analysis*; D007201:Indicator Dilution Techniques; D007700:Kinetics; D007834:Lasers; D008715:Methionine / Q000737:chemistry / Q000494:pharmacology; D008958:Models, Molecular; D009994:Osmolar Concentration; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry / Q000528:radiation effects*; D010782:Photolysis / Q000187:drug effects; D011506:Proteins / Q000737:chemistry / Q000528:radiation effects*; D011829:Radiation Dosage
chemical_list: D016166:Free Radical Scavengers; D016877:Oxidants; D011506:Proteins; D005973:Glutamine; D017665:Hydroxyl Radical; D010649:Phenylalanine; D006639:Histidine; D008715:Methionine; D003903:Deuterium; D006861:Hydrogen Peroxide