Radiation-induced structural changes in model lipid membranes

The effect of gamma-irradiation on the structure of model membranes prepared from egg-yolk phosphatidylcholine was followed by electron spin resonance and fluorescence spectroscopy. Irradiation of membrane suspensions was found to produce differential effects in polar and hydrophobic regions of the lipid bilayer. The polar head group regions become less ordered than monitored by the decrease in order parameter of membrane-incorporated 5-doxylstearic acid spin-label. This is accompanied by an increase in microviscosity of membrane inner hydrocarbon regions as reflected in the reduced mobility of two hydrophobic probes, pyrene and 12-doxylstearic acid methyl ester. The structural modifications of model bilayers following gamma-irradiation are compared with those reported for biological membranes. (author)