NMR Experiments on Ion Permeation in Irradiated Model Membranes

In aqueous solutions of sonicated egg-lecithin vesicles (5 weight-%) the 1H-NMR parameters line width, area, and chemical shift of the signal of the (CH3)3N+ group were determined in dependence on the dose of gamma radiation (0 … 12 kGy). The application of curopium ions made it possible, by means of a line shape analysis, to calculate these parameters for the inside as well as for the outside lipid layer. With increasing 60Co-radiation dose the line widths increase linearly. The line width for the outside lipid layer increases significantly more rapidly than for the inside layer. This fact allows us to conclude that there exists a preferred radiation damage of the outside lipid layer. The asymmetry may he a consequence of an indirect radiation action mediated by the radicals of the water radiolysis. From the temporal change of the NMR parameters information can be obtained about the radiation action on transport processes in the vesicles. Beginning at a threshold value (approx. 5 kGy) the permeation of t...