THE INCREASE OF MEMBRANE CAPACITANCE AS A CONSEQUENCE OF RADIATION-INDUCED LIPID-PEROXIDATION

The electrical capacitance of lipid membranes may increase by up to 50% on exposure to ionizing radiation. This is the consequence of lipid peroxidation induced by primary or secondary radicals of water radiolysis in the presence of oxygen. The polar products of this process give rise to an increase of the dielectric constant of the membrane. This in turn leads to the increase of membrane capacitance observed. An important consequence of this phenomenon is the reduction of the inner energy barrier between the two membrane/water interfaces influencing the movement of charged particles across the membrane. Thus the comparatively small change of the dielectric constant gives rise to the large increase in membrane conductance (by up to several orders of magnitude) observed in the presence of macrocyclic ion carriers of the valinomycin type (Strassle et al. 1987b). The results were obtained applying a novel method to measure time-dependent changes of the capacitance of planar lipid membranes.