Journal of Lipid Research, Vol 23, 994-1000, Copyright © 1982 by Lipid Research, Inc.
Decomposing potassium peroxychromate produces hydroxyl radical (.OH) that can peroxidize the unsaturated fatty acids of phospholipid dispersions
JC Edwards and PJ Quinn
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.
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