Analysis of mixtures of polyanions with bovine serum albumin by size exclusion chromatography with quadruple detection method

Water-soluble and insoluble protein-polyelectrolyte complexes as functional biopolymersystems represent a specific class of polymer-protein compounds that have importantapplications in various areas. The extent of the interaction of polyelectrolytes (PE) withproteins in aqueous solutions is found to be pH and ionic strength sensitive and dependent onthe isoelectric points of proteins. Polymer-protein complexes form as a result of theelectrostatic interaction of polyion chains with the oppositely charged groups of the proteinmolecule during these reactions.In this study, we attempt to investigate the interaction of bovine serum albumin (BSA) withpolyacrylic acid (PAA) and molecular properties of soluble polyelectrolyte complexes atdifferent ratios of components (nBSA/nPAA=0,5-50) and pH of solutions (pH=4,0; 4,3; 5,0; 6,0;7,0) using size-exclusion chromatography (SEC) with on-line quadruple detection system: UVabsorption (UV), refractive index (RI), light scattering (LS) and viscosity (VIS) detectors.While interaction between polyanion and protein is not observed at neutral pH values, stablewater-soluble complexes form at pH values close to isoelectric point of BSA. Investigation ofphysicochemical behaviors of these soluble complexes by chromatography shows thatmolecular weight and size of polycomplex particles passes through a maximum molar ratiorange. At pH values below the isoelectric point of protein, water-insoluble complexes form asa result of strong electrostatic attraction. After centrifugation, supernatants were analysed. Atvery low and high values of molar ratios, water-soluble polyanion-protein complexes formand it was showed that these soluble complexes coexist with water-insoluble complexes. Atfirst step, aggregation occurs between polyelectrolyte-protein complexes before precipitationKey words: polyelectrolyte-protein complexes, size exclusion chromatography, lightscattering, viscometry.