A reaction between the superoxide free radical and lipid hydroperoxide in sodium linoleate micelles

The oxidation of unsaturated fatty acid micelles by the superoxide free radical (O^{{minus sign, dot below}} ₂), during γ irradiation in the presence of formate, is kinetically distinct from oxidation by hydroxyl free radicals (HO.). The evidence suggests that a direct reaction between (O^{{minus sign, dot below}} ₂) and lipid hydroperoxide initiates a chain oxidation process in the micelles. While tetranitromethane, which reacts rapidly with (O^{{minus sign, dot below}} ₂), protects the micelles from oxidation, active superoxide dismutase is no more effective than its apoprotein, due to lack of penetration of the micellar environment. We discuss these findings in the light of recent literature, and with reference to their possible significance for biological systems.