Charge Transfer Processes in Model and Biological Membranes: Defect and Mechano-Electric Aspects; Statics and Dynamics

Abstract

Mechano-electricity is a fundamental property of membranes, related to their mechanical and electrical degrees of freedom. Special importance in this respect is paid to the following pairs of variables: membrane tension and conducting defects' state; membrane curvature and polarization. Charge transfer processes are profoundly influenced by the interrelation between the tilted membrane characteristics. The effect of membrane tension on the probability of opening of ion channels in locust muscle membrane has been studied using patch clamp techniques. The data emanating from these studies are consistent with a linear model of stress activation of these channels. Mechanosensitive defects (ion pores) in model dip-tip lecithin membrances containing peptide cyanobacterial toxins (microcystin and nodularin) have also been studied. In this case application of tension caused a progressive opening of defect states of higher conductance, according to a model for pore gating by lateral tension. Membrane curvature is related to another fundamental mechano-electnc property of membranes, viz. curvature electricity or flexoelectricity. By using patch clamp techniques combined with phase-sensitive amplification and by dynamic excitation of natural and artificial membranes by oscillating pressure it has been possible to study flexoelectric effects without and with ion pores or channels in the membranes. Striking enhancement of the flexoelectric res- ponse during pore/channel opening was observed. These data provide the first experimental evidence of our hypothesis that flexoelectricity is a driving force for ion transport through membrane channels.