Determination of some solubilization parameters with surfactants of egg-yolk lecithin multilamellar vesicles by static light-scattering measurements

Abstract

Effective surfactant:phospholipid ratios (i.e. molar ratios in the mixed aggregates, vesicles or micelles) have been determined by static light-scattering for the interaction of egg-yolk lecithin (EYL) multilamellar vesicles (MLV) with Triton X-100 (TX-100), sodium deoxycholate (DOCNa) and cetyltrimethylammonium bromide (CTMB). The suspension of MLV-EYL was mixed with appropriate volumes of surfactant solution and was left overnight to reaches thermodynamic equilibrium. Rectan-gular optic diffusion data were used to compute the solubilization parameters: total surfactant concentrations, at saturation and solubilization Dtsat and Dtsol respectively, and effective molar ratios, Resat and Resol respectively. From the Resat value ob-tained graphically for interaction of vesicles with TX-100 resulted that in vesicle bilayers a surfactant molecule is surrounded with seven phospholipid molecules and the Resol value suggests that in mixed micelles ten lipid molecules with about fifteen surfactant molecules coexist. The values of Resat and Resol in case of MLV solubilization with DOCNa are 0.07 and 1.1 re-spectively. In case of vesicles solubilization with CTMB, Resat =0.25 and Resol =3.6 These data show that the solubilization power at thermodynamic equilibrium for the three surfactants is in the sequence: CTMB<TX-100<DOCNa.