Site-specific induction of lipid peroxidation by iron in charged micelles

Generation of hydroxyl radicals by the Fenton reaction resulted in lipid peroxidation of linoleic acid (LA) (H₂O₂-Fe²⁺-induced lipid peroxidation) in positively charged tetradecyltrimethylammonium bromide (TTAB) micelles, but not in negatively charged sodium dodecyl sulfate (SDS) micelles. However, more OH radicals formed via the Fenton reaction were trapped by N-t-butyl-α-phenylnitrone (PBN) in SDS micelles than in TTAB micelles. When detergent-dispersed LA was contaminated with linoleic acid hydroperoxide (LOOH), lipid peroxidation was catalyzed by Fe²⁺ via reductive cleavage of LOOH (LOOHFe²⁺-induced lipid peroxidation), and Fe²⁺ was oxidized simultaneously in SDS micelles, even when H₂O₂ was not present. In contrast, LOOHFe²⁺-induced lipid peroxidation and simultaneous oxidation of Fe²⁺ were not observed in TTAB micelles. An ESR spectrum presumed to be due to an alkoxy radical trapped by PBN was also detected in SDS micelles, but not in TTAB micelles in the LOOHFe²⁺-induced lipid peroxidation system. The results are discussed in the light of the localization of iron, the unsaturated bonding moiety of LA, the OOH-group of LOOH, and the trapping site of PBN in different charged micelles.