THE INTERACTIONS IN SOLUTION BETWEEN NONIONIC SURFACTANTS AND GLOBULAR-PROTEINS - EFFECTS ON CLOUD POINT

The effects of protein addition (lysozyme and bovine serum albumin) on surface tension reduction and cloud point of a surfactant (Pentaethyl eneglycol Mono n-Dodecyl Ether (C12E5)) were studied. The minimum surf ace tension was in all cases 27 mN/m but was reached at a higher surfa ctant concentration for the BSA/C12E5 solution than for the pure surfa ctant or the lysozyme/surfactant mixture, indicating that C12E5 binds to BSA but not to lysozyme. It was estimated that BSA bound four to fi ve molecules of C12E5. Only BSA seemed to have any large effect on the cloud point of the surfactant and above a certain critical protein to surfactant ratio the clouding is totally suppressed. The results impl ies that the presence of protein influences the clouding only if surfa ctant binds to the protein.