Biopolymer–surfactant interactions: 5: Equilibrium studies on the binding of cetyltrimethyl ammonium bromide and sodium dodecyl sulfate with bovine serum albumin, β-lactoglobulin, hemoglobin, gelatin, lysozyme and deoxyribonucleic acid

Abstract

The equilibrium binding of cetyltrimethyl ammonium bromide (CTAB) with bovine serum albumin, β-lactoglobulin, hemoglobin, lysozyme, gelatin and deoxyribonucleic acid, and of sodium dodecyl sulfate (SDS) with lysozyme, has been studied by an electrometric method mainly with variation of pH and ionic strength. The reversibility of the interaction has been established by studying the association and dissociation processes. The isotherms obtained are of the co-operative type; DNA, β-lactoglobulin and bovine serum albumin have shown strong binding of CTAB; the binding of SDS with lysozyme is also fairly strong and greater than that of CTAB. Ionic strength and pH influence the interaction process. The free energies of binding are distinctly of two categories. The low and high free energies (Δ G I° and Δ G II°) correspond to normal and co-operative binding processes respectively, their difference being identified with the free energy of co-operative association.