Effect of radiation induced lipid peroxidation on diphenylhexatriene fluorescence in egg phospholipid liposomal membrane.

Ionizing radiation induced chemical/structural modification in liposomes and related changes in fluorescence intensity of incorporated 1,6-diphenyl 1,3,5-hexatriene (DPH) was investigated in egg lecithin unilamellar vesicles. A correlation was found to exist between the magnitude of malondialdehyde (MDA) formation and the fluorescence decay of incorporated DPH in liposomal membrane after gamma-radiation. The reduction of DPH fluorescence and formation of MDA following radiation were significantly affected when alpha-tocopherol was incorporated into the liposomes. The observed effects of alpha-tocopherol were found to be dependent on its concentration in the liposome. A marked difference in emission spectra of DPH was found on radiation of liposomes prepared with the probe compared with that obtained from the labeling of liposomes after radiation depending on the applied radiation dose. The observed reduction in quantum yield of DPH in radiated liposomes is interpreted in terms of its environmental changes to a greater polarity. These results suggest that DPH fluorescence may provide an index of radiation induced lipid peroxidation caused by free radical reaction in unilamellar lecithin liposomes.