Interaction between model membranes and a new class of surfactants with antioxidant function

The effect of two series of amphiphilic quaternary ammonium salts on some properties of phospholipid membranes was studied. The compds. of one series, N-benzyl-N,N-dimethyl-N-alkyl ammonium bromides, exert a destructive effect on membranes and are treated as ref. compds. The compds. of the other series, N-(3,5-di-t-butyl-4-hydroxy)benzyl-N,N-dimethyl-N-alkyl ammonium bromides, are derivs. of the former ones, exhibit antioxidant properties, and do only relatively slight damage to the membranes. The aim of the work was to explain the difference in mol. interaction with membranes between the two kinds of hydrophobic compds. Thermodn. methods, a new mixing technique, and monolayer and quantum calcn. methods were used. It has been shown that the antioxidant mols. are less hydrophobic than those of the ref. compds. and disturb the membrane organization to a lesser extent. On the basis of monolayer data, the authors suggest that the studied antioxidant behaves like a substitutional impurity, whereas the ref. behaves like an interstitial one.