INTERACTION OF NATURAL AND SYNTHETIC POLYELECTROLYTES WITH BOVINE SERUM ALBUMIN

Abstract

Interaction of a number of natural and synthetic polyelectrolytes (PE): chitosan, poly‒N,N‒dimethyl‒N,N‒diallylammonium chloride, sodium carboxymethylcellulose and aromatic copolyamide, synthesized on the bases of dichloranhydride of isophthalic acid and two diamines (4,4’‒(2,2’‒sodium disulfonate)‒diaminodephenyl, 4,4’‒(2,2’‒dicarboxylic acid)‒diaminodiphenylmethyl) and bovine serum albumin (BSA) in aqueous solutions were studied. It was shown that as a result of macromolecular reactions protein‒polyelectrolyte complexes (PPC) forms, stabilized mainly by electrostatic forces. To characterize their composition we used the value of parameter φ, defined as an amount of ionic groups of polyelectrolytes calculated per macromolecule of protein. Using spectrophotometry and conductometry it was established that the composition of PPC in the studied systems when components are mixed at optimal conditions corresponds to the value of φ ~30 – 90. The conditions for the existence of insoluble PPC were determined. In the case of precipitation of poly-N,N‒dimethyl‒N,N‒diallylammonium chloride and chitosan in protein – polyelectrolyte reactions the maximum yield of the product is observed at pH ≥ 7. The introduction of sodium carboxymethylcellulose and aromatic copolyamide into the interaction with protein accompanied by shifting the range of PPC existence into the acidic region: the maximum yield of the product is observed at рН ≤ 4. The size of the formed complex particles ranges from 10 nm ([PE]/[BSA] = 0.01 – 0.05 g/g) to ~ 1.0 ‒ 5.5 μm ([PE]/[BSA] = 0.1 – 0.35 g/g). In case of relatively short‒chained aromatic copolyamide, containing significant amount of non‒ionized carboxylic groups, the ratio of micron size particles is about 5%. The presence of sulfonate and carboxylic groups in the composition of copolyamide gives an additional opportunity to regulate the conversation degree in the interpolyelectrolyte reactions, thus also implying the structure and the composition of the formed complexes.