Counterion effects on interaction of amphiphilic quaternary ammonium saltswith model membranes

The micellization as well as the interaction with model membranes of dodecy ltrimethylammonium halides (DTAX) and N-dodecyl-N,N-dimethyl-N-benzylammoni um halides (DBeAX) were studied at 298K and 313K by means of titration calo rimetry. The calorimetric curves reflect both the counterion and benzyl gro up effects on the interaction of the surfactants studied with the lipid bil ayer. Bromide as counterion enhanced the interactions more than chloride of both DTAX and DBeAX compounds with model membranes. Further. we studied the influence of DTAX and DBeAX on calcium ion desorpti on from the liposome membrane using a radioactive tracer method. DBeAX prov ed more efficient in desorption of calcium than DTAX. Iodides of these comp ounds enhanced this process more than bromides and chlorides.