title: Direct evidence of singlet molecular oxygen [O2(1Deltag)] production in the reaction of linoleic acid hydroperoxide with peroxynitrite.
abstract: Peroxynitrite (ONOO-), a biologically active species, can induce lipid peroxidation in biological membranes, thereby leading to the formation of various hydroperoxides. We report herein on the formation of singlet molecular oxygen [O(2) ((1)Delta(g))] in the reaction of peroxynitrite with linoleic acid hydroperoxide (LAOOH) or (18)O-labeled LAOOH. The formation of O(2) ((1)Delta(g)) was characterized by (i) dimol light emission in the red spectral region (lambda > 570 nm) using a red-sensitive photomultiplier; (ii) monomol light emission in the near-infrared region (lambda = 1270 nm) with a liquid nitrogen-cooled germanium diode or a photomultiplier coupled to a monochromator; (iii) the enhacing effect of deuterium oxide on chemiluminescence intensity, as well as the quenching effect of sodium azide; and (iv) chemical trapping of O(2) ((1)Delta(g)) or (18)O-labeled O(2) ((1)Delta(g)) with the 9,10-diphenylanthracene (DPA) and detection of the corresponding DPAO(2) or (18)O-labeled DPA endoperoxide by HPLC coupled to tandem mass spectrometry. Moreover, the presence of O(2) ((1)Delta(g)) was unequivocally demonstrated by a direct spectral characterization of the near-infrared light emission attributed to the transition of O(2) ((1)Delta(g)) to the triplet ground state. For the sake of comparison, O(2) ((1)Delta(g)) deriving from the thermolysis of the endoperoxide of 1,4-dimethylnaphthalene or from the H(2)O(2)/hypochlorite and H(2)O(2)/molybdate systems were also monitored. These novel observations identified the generation of O(2) ((1)Delta(g)) in the reaction of LAOOH with peroxynitrite, suggesting a potential O(2) ((1)Delta(g))-dependent mechanism that contributes to cytotoxicity mediated by lipid hydroperoxides and peroxynitrite reactions in biological systems.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970, São Paulo, SP, Brazil.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Glaucia R
authors.initials: GR
authors.lastname: Martinez
authors.forename: Ana Paula B
authors.initials: AP
authors.lastname: Martins
authors.forename: Marisa H G
authors.initials: MH
authors.lastname: Medeiros
authors.forename: Paolo
authors.initials: P
authors.lastname: Di Mascio
mesh_terms: D002851:Chromatography, High Pressure Liquid; D008041:Linoleic Acids / Q000737:chemistry*; D008054:Lipid Peroxides / Q000737:chemistry*; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods
chemical_list: D008041:Linoleic Acids; D008054:Lipid Peroxides; D030421:Peroxynitrous Acid; D026082:Singlet Oxygen; C008285:linoleic acid hydroperoxide