The Langmur-blodgett monolayer dipole potential: a smeared dipole model for a lipid array, and pulsing of the potential by direct subphase infusion of immunochemical and lecti/polysaccharide complexes

Abstract

An important contribution to the surface potential of lipid bilayers and monolayers comes from the intrinsic dipole moment of the lipid molecules. A theoretical model of the monolayer which involves a smeared dipole sheet approximation is introduced. This model is used to explore the nature and origins of the surface potential. In addition, the potential associated with phosphatidyl choline/cholesterol monolayers compressed on a Langmuir-Blodgett trough was measured with a non-contacting electrostatic voltmeter. A trough infusion configuration was fabricated to perform dynamic subphase experiments with compressed films in place. The potential/time response of monolayers to selective bimolecular systems such as antibody-antigen and concanavalin A-saccharide pairs was examined. These reactions induce spontaneous transients in dipole potential of magnitude 20–80 mV and duration of less than 1 s. The potential transients are attributed to local perturbation of lipid orientation and introduction of protein dipole fields caused by the formation of aggregates at the monolayer/water interface.