The effect of undecaprenol on bilayer lipid membranes.

The influence of undecaprenol on phosphatidylcholine macrovesicular bilayer lipid membranes has been studied by electrophysiological techniques. The current-voltage characteristics, ionic transference numbers, the membrane conductance-temperature relationships and the membrane breakdown voltage were measured. The permeability coefficients for Na+ and Cl- ions, the activation energy of ion migration across the membrane, the membrane hydrophobic thickness and the membrane Young's modulus were determined. Undecaprenol increases membrane conductance, membrane capacitance, membrane ionic permeability and membrane elastic deformability, decreases the activation energy, membrane hydrophobic thickness and membrane electromechanical stability, and does not change membrane selectivity. The formation by undecaprenyl molecules of fluid microdomains modulating membrane hydrophobic thickness is postulated. The data suggest that the behaviour of undecaprenol in membranes is regulated by transmembrane electrical potential.