The investigation of water soluble complexes and covalent conjugates of bovine serum albumin with polyacrylic acid by HPLC method

The complexes and covalent conjugates of synthetic polyanions with proteins appear to be ofgreat importance for bioengineering, medicine and different areas on basic science. Thissystems can be considered as a model of antigen-antibody interaction, specific nucleoproteincomplexes and nucleotid-protein complexes, in particular supplying us with novel informationon immunogenic compounds for synhetic vaccine innovation.Polymer-protein complexes form as a result of the electrostatic interaction of polyion chainswith the oppositely charged groups of the protein molecules. To find out the mechanism ofthe polycomplex formation and structure of forming particles as well as the transition ofsoluble polycomplexes to insoluble state, water-soluble mixtures and matrix solutions ofinsoluble BSA-PAA complexes investigated by pH titration, spectrometric and HPLCmethods. It was shown that the complex formation and the phase state of the systems dependson pH of the solution and ratio of components. Polyacrylic acid (PAA) and bovine serumalbumine (BSA) form polymer-protein complexes which are water soluble or insolubledepending on pH values (pH=4.0-7.0) and a wide range of protein/polymer ratios(nBSA/nPAA=0.05-50). The stability of PAA-BSA complexes at pH > pI is negligible weak (pH7.0), at the same time decreasing of pH (pH < pI) results with increasing of the stability ofpolycomplex particles and it was established that formation of polycomplexes have differentphysicochemical and conformational properties at a wide range of nBSA/nPAA ratios (pH 5.0).Existence of water-insoluble PAA-BSA complexes have been observed at pH 4.0. It was firsttime transition of soluble polycomplexes to insoluble state have been stated and binding modeof polyelectrolytes to proteins is assumed to be dependent on the ratio of components as aresult in formation of soluble polycomplexes, complex coacervation or amorphousprecipitates.Key words: polyelectrolyte, polyacrylic acid, bovine serum albumin, phase separation, gelpermeation chromatography