THE ROLE OF COUNTERIONS IN THE INTERACTION OF BIFUNCTIONAL SURFACE-ACTIVE COMPOUNDS WITH MODEL MEMBRANES

Interaction of two series of bifunctional surfactants (bromides and ch lorides) with red blood cells and planar lipid membranes was studied. The aim of the work was to determine the role of counterions in the me chanism of interaction of bifunctional cationic surfactants with model membranes. In each case bromides influenced model membranes to a grea ter degree than the corresponding chlorides. The possible explanation of the obtained results is presented. It seems that the greater abilit y of bromides to destabilize model membranes in comparison with chlori des can be attributed to the greater mobility and the smaller radius o f the hydrated bromide ion. This may underlie the greater ease that th is anion can modify the surface potential of the lipid bilayer, thus e nhancing the interaction of the cationic surfactant with such a modifi ed bilayer.