Protein-surfactant Interaction Research Articles

The application of monolayer techniques to a study of protein-surfactant interaction: I. Interactions in spread films at the air/water interface

Monolayer properties (surface pressure, potential, viscosity, and elasticity) of a number of protein films have been measured in the presence of cationic and anionic surfactants. The proteins studied were bovine serum albumin, hemoglobin, lysozyme, pepsin, and trypsin, which were spread alone and together with various quantities of n-octadecyl trimethylammonium bromide, n-docosyl trimethylammonium bromide, or sodium n-octadecyl sulfate. The combinations of proteins and surfactants and the experimental conditions employed were selected so that the mixed films could be studied over as wide a range of molecular charge conditions as possible. In all cases it was observed that expansion of the protein surface pressure/area curve occurred in the presence of surfactant. Surface potentials were increased in the presence of cationic surfactant but the anionic material caused a decrease. A most interesting feature was that surface viscosity and elasticity were greatly reduced in all the systems studied. The reasons for these observed changes in surface parameters are discussed in terms of the state of molecular packing present in the mixed films and the possible effects of surfactant ions on the bonding forces present in protein monolayers.