Influence of polyelectrolyte on dynamic surface properties of BSA solutions

The dynamic surface elasticity of mixed solutions of bovine serum albumin (BSA) and poly(diallyldimethylammonium chloride) (PDADMAC) was measured as a function of the surface age, polyelectrolyte concentration and solution pH. The addition of polyelectrolyte does not influence the dynamic surface properties of protein solution at pH below the isoelectric point of BSA. At the same time, one can observe significant changes of the kinetic dependencies of the surface pressure and surface elasticity under the influence of polyelectrolyte at higher pH indicating the interaction between the components. The acceleration of the changes of the surface properties can be connected with the decrease of the electric adsorption barrier due to the decrease of the total charge of the protein/polyelectrolyte complex. The local maximum of the kinetic dependencies of the dynamic surface elasticity at pH higher than the isoelectric point indicates partial destruction of the protein tertiary structure at high surface pressures.