title: Decomposing potassium peroxychromate produces hydroxyl radical (.OH) that can peroxidize the unsaturated fatty acids of phospholipid dispersions.
abstract: The unsaturated fatty acyl residues of egg yolk lecithin are selectively removed when bilayer dispersions of the lipid are exposed to decomposing peroxychromate at pH 7.6 or pH 9.0. Mannitol (50 mM or 100 mM)partially prevents the oxidation of the phospholipid due to decomposing peroxychromate at pH 7.6 and the amount of lipid lost is inversely proportional to the concentration of mannitol. N,N-Dimethyl-p-nitrosoaniline, mixed with the lipid in a molar ratio of 1.3:1, completely prevents the oxidation of lipid due to decomposing peroxychromate at pH 9.0, but some linoleic acid is lost if the incubation is done at pH 7.6. If the concentration of this quench reagent is reduced tenfold, oxidation of linoleic acid by decomposing peroxychromate at pH 9.0 is observed. Hydrogen peroxide is capable of oxidizing the unsaturated fatty acids of lecithin dispersions. Catalase or boiled catalase (2 mg/ml) protects the lipid from oxidation due to decomposing peroxychromate at pH 7.6 to approximately the same extent, but their protective effect is believed to be due to the non-specific removal of .OH. It is concluded that .OH is the species responsible for the lipid oxidation caused by decomposing peroxychromate. This is consistent with the observed bleaching of N,N-dimethyl-p-nitrosoanaline and the formation of a characteristic paramagnetic .OH adduct of the spin trap, 5,5-dimethylpyrroline-1-oxide.
mesh_terms: D002374:Catalase; D055598:Chemical Phenomena; D002621:Chemistry; D002840:Chromates; D004578:Electron Spin Resonance Spectroscopy; D005231:Fatty Acids, Unsaturated; D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; D008081:Liposomes; D010545:Peroxides; D010713:Phosphatidylcholines; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002840:Chromates; D005231:Fatty Acids, Unsaturated; D005609:Free Radicals; D006878:Hydroxides; D008081:Liposomes; D010545:Peroxides; D010713:Phosphatidylcholines; C019537:potassium tetraperoxochromate; D017665:Hydroxyl Radical; D002374:Catalase