Significance of amino groups of phosphatidylethanolamine in phospholipid peroxidation of mixed liposomes.

The effect of distribution of phosphatidylethanolamine (PE) in multilamellar vesicles (MLV) on their peroxidative susceptibility was studied. Liposomes containing various ratios of L-alpha-dilinoleoyl phosphatidylcholine (DiLinPC) and L-alpha-dilinoleoyl phosphatidylethanolamine (DiLinPE) were peroxidized by ferrous ion or a water-soluble radical initiator 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH). The oxygen consumption rate was compared with the formation kinetics of fluorescent products. Inclusion of PE in liposomes was found to accelerate the Fe(2+)-dependent peroxidation. Modification of the amino group of PE with 2,4,6-trinitrobenzenesulfonic acid (TNBS) inhibited Fe(2+)-induced oxygen consumption in the late stage where fluorescent substances formed. A possible role of the amino group of PE on lipid peroxidation is discussed, especially in terms of its reactivity with oxidation products and subsequent formation of fluorescent substances.