Effect of products of radiation-induced free radical fragmentation of phospholipids and temperature on lipid membranes

Thermotropic behavior of liposomes exposed to gamma -radiation was studied by differential scanning microcalorimetry. It was found that the peak corre sponding to the gel-liquid crystal transition for liposomes composed of bov ine brain sphingomyelin and dipalmitoyl phosphatidylglycerol broadened and shifted toward the high-temperature region. No effect of irradiation on dip almitoyl phosphatidylcholine liposomes was observed. Previously it was show n that, on exposure to gamma -rays, sphingomyelin and phosphatidylglycerol, as opposed to phosphatidylcholine, broke down into fragments of lower mole cular weight. It is concluded that the accumulation of products of phosphol ipid fragmentation in the membrane results in the changes of phase transiti on parameters.