Redistribution of positively charged probes in membrane suspension under the action of transmembrane potential.

The distribution of amphiphilic and hydrophobic positively charged probes in suspensions of closed membrane vesicles was analysed by the methods of equilibrium thermodynamics. Two versions of the probe location in the membranes are discussed: near the boundary between the polar and hydrocarbon regions, and in the centre of the hydrocarbon region of a lipid bilayer. It is shown that, in the first case, the action of the inside-negative transmembrane potential results in an increased average probe concentration in the lipid phase and in a significant redistribution of the probe in the membrane interior. An inside-positive transmembrane potential causes a decrease in the average probe concentration in membranes, the probe being redistributed in the membrane bilayer. If the probe is sited in the centre of the hydrocarbon layer, the transmembrane potential evokes only an increase or decrease in the probe concentration in membranes at a negative or positive sign of the potential inside the vesicles.