Complexationof Globular Proteins with surfactants mixtures

ELENA BLANCO, PAULA V. MESSINA, JUAN SABIN, JUAN M. RUSO, GERARDO PRIETO, FÉLIX SARMIENTO

Budapest, Hungary

Conferencia; 20th Conference of the European Colloid and Interface Society and 18th European Chemistry at Interfaces Conference; 2006

Colloid and Material Chemistry Division of Hungarian Academy of Sciences and Department of Colloid Chemistry, University of Szeged

The complexations between human serum albumin (HSA) and the sodium perfluorooctanoate/ sodium octanoate and sodium perfluorooctanoate/ sodium dodecanoate systems have been studied by a combination of electrical conductivity, ion-selective electrode, electrophoresis and spectroscopy measurements. The binary mixtures of the surfactants deviated slightly from ideality. Binding plots revealed the existence of two specific binding sites, being the first site being more accesible than the second. Positively co-operative binding has been found, thus revealing the importance of the hydrophobic interactions in both kinds of surfactants. The Gibbs energies of binding per mole of surfactant were calculated from the Wyman binding potential where, based on the elevated number of binding sites, a statistical contribution has been included. Initially these energies are large and negative, gradually decreasing as saturation is approached. Changes in the slope of Gibbs energies have been identified with the saturation of the first binding set. These facts denote that the surfactants under study have different favorite adsorption sites  along the protein and the adsorption process of perfluorooctanoate is more closely followed by dodecanoate than by octanoate. Finally, electrophoresis and spectroscopy measurements suggest induced conformational changes on HSA depending on the surfactant mixture as well as the mixed ratio.