ABSTRACT
We examine whether a small amount of strong polyelectrolyte (dextran sulfate sodium (DSS) salt) can induce mixing of bovine serum albumin (BSA) and dextran in aqueous water-in-water BSA/dextran emulsion and how intermacromolecular interactions affect its the rheological properties. Addition of DSS to water-in-water emulsion at pH 5.4 leads to its mixing, a noticeable increase in viscosity and module (G′). Mixing is observed at the DSS/BSA weight ratio, qBSA ≥ 0.07. Increasing the ionic strength in the resulting single-phase system induces phase separation. Our results show that the increase in viscoelasticity results from the interaction of DSS with both macromolecular components. The interaction of DSS with BSA leads to the screening of BSA tryptophanyls from the aqueous environment. Such interaction is not accompanied by the polarization of the protein, whereas the affinity of DSS to dextran results in an increase of viscoelasticity and in an appreciable change in the microstructure of the DSS/dextran mixture. It was assumed that similar to compatibilization of polymer blends by diblock copolymers, the driving force for inducing mixing of water/BSA/ dextran emulsions by DSS results from the affinity of strong polyelectrolytes to both macromolecular components of the mixture.
