A polycation causes migration of negatively charged phospholipids from the inner to outer leaflet of the liposomal membrane.

Aggregation of the negatively charged liposomes caused by the addition of the linear polycation, poly-N-ethyl-4-vinylpyridine bromide, was studied. At the point of maximal size and zero electrophoretic mobility of aggregates, the concentration of positive charges brought in by the adsorbed polycation was found to be equal to the total concentration of negative charges both on the outer and inner surface of the lipid bilayer. Since polycation saturation of the liposomal negative charges was found to occur without disruption of the membrane, it was concluded that the polycation induced migration of negatively charged phospholipid molecules from the inner to outer leaflet of the bilayer.