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 [O2 (1Δg)] in the reaction of peroxynitrite with linoleic acid hydroperoxide (LAOOH) or 18O-labeled LAOOH. The formation of O2 (1Δg) was characterized by (i) dimol light emission in the red spectral region (λ > 570 nm) using a red-sensitive photomultiplier; (ii) monomol light emission in the near-infrared region (λ = 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 O2 (1Δg) or 18O-labeled O2 (1Δg) with the 9,10-diphenylanthracene (DPA) and detection of the corresponding DPAO2 or 18O-labeled DPA endoperoxide by HPLC coupled to tandem mass spectrometry.
Moreover, the presence of O2 (1Δg) was unequivocally demonstrated by a direct spectral characterization of the near-infrared light emission attributed to the transition of O2 (1Δg) to the triplet ground state. For the sake of comparison, O2 (1Δg) deriving from the thermolysis of the endoperoxide of 1,4-dimethylnaphthalene or from the H2O2/hypochlorite and H2O2/molybdate systems were also monitored. These novel observations identified the generation of O2 (1Δg) in the reaction of LAOOH with peroxynitrite, suggesting a potential O2 (1Δg)-dependent mechanism that contributes to cytotoxicity mediated by lipid hydroperoxides and peroxynitrite reactions in biological systems.
Miyamoto, S., Martinez, G.R., Martins, A.P.B., Medeiros, M.H. and Di Mascio, P., 2003. Direct evidence of singlet molecular oxygen [O2 (1Δg)] production in the reaction of linoleic acid hydroperoxide with peroxynitrite. Journal of the American Chemical Society, 125(15), pp.4510-4517.
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