ELECTRIC-FIELD-INDUCED CONCENTRATION GRADIENTS IN LIPID MONOLAYERS

Externally applied electric field gradients gave rise to lateral conce ntration gradients in monolayers of certain binary lipid mixtures. For binary mixtures of dihydrocholesterol and dimyristoylphosphatidylchol ine, the application of an electric field gradient at pressures below the critical pressure produced a liquid-liquid phase separation in a m onolayer that is otherwise homogenous. At pressures slightly above the critical pressure, a field gradient produced a large concentration gr adient without phase separation. The lipid concentration gradients can be described by equilibrium thermodynamic chemical potentials. The ob served effects appear to be relevant to the structure and composition of biological membranes.