The structure of unsaturated lipid dispersions in aqueous systems influences susceptibility to oxidation

The susceptibility of unsaturated lipids dispersed in aqueous systems to oxidation in the presence of decomposing peroxychromate has been examined. Almost complete oxidation of unsaturated monoenoic fatty acyl residues present in detergents such as Tween 80, which form micellar structures, was observed, whereas multibilayer liposomes of egg-yolk phosphatidylcholine could be oxidized only partially despite the presence of more susceptible polyenoic fatty acids. More vigorous methods of phospholipid dispersion or disturbing the structure of partially oxidize dispersions increased susceptibility of peroxidation, suggesting that substrate molecules located in the centre of large multibilayer dispersions are not accessible to free radicals generated in the bulk water.