The effects of SDS at subsolubilizing concentrations on the planar lipid bilayer permeability: Two kinds of current fluctuations

Detergent effects on lipid bilayers of artificial and biological membranes at subsolubilizing concentrations are known to include the membrane permeabilization which manifests itself through both a flip-flop of detergent molecules from the outer monolayer to the inner monolayer and the membrane leakage of entrapped solutes. We have explored the current fluctuations occurring in planar BLM of asolectin in the presence of ionic detergent SDS at subsolubilizing concentration. Two groups of current fluctuations which the average duration differs by two orders of magnitude can be distinguished. We assume that these differences in the duration of current fluctuations are associated with a different number of SDS molecules in the walls of the putative toroidal hydrophilic pores. We associated short pulses with the formation of short-lived lipid hydrophilic pores. Impulses of greater duration (steps) were associated with the formation of hydrophilic pores, the walls of which contain detergent. Taking into account the characteristics of these pores, we estimated the pore energy, as well as the edge energy of these two kinds of pores. We believe that the flip-flop of SDS molecules in liposomes is provided by long-lived pores, and the contents of the liposome leakage occurs through all pores.