Radio-frequency dielectric spectroscopy of synthetic bilayers containing glycolipids

The electrical conductivity of aqueous solutions of colloidal phospholipid-ganglioside mixtures has been measured in the frequency range from 10 kHz to 100 MHz, where a conductivity dispersion due to the interfacial polarization occurs. Insertion of GM1 ganglioside in the phospholipid bilayer alters markedly the electrical behaviour of the whole suspension that exhibits some interesting features, which depend on the GM1 concentration. In a restricted range of the ganglioside concentration, the experimental data can be partially explained by introducing a surface conductivity contribution in the usual conductivity theory of heterogeneous systems. Although preliminary, these measurements indicate that gangliosides, according to the structural shape they assume, modify the electrical properties of the lipid bilayer. This effect may be relevant to understanding ganglioside interactions with lipid components of biological cell membranes.