Polyelectrolyte complexes as vehicles for affinity precipitation of proteins

Polyelectrolyte complexes (PECs) were formed with polyethylene imine (PEI) and polyacrylic acid sodium salt (PA), The aqueous solubility of such PECs is dependent on the stoichiometry between the polymers, the charge densities of the polymers and salts present in the solution. Cibacron blue 3GA (CB) was coupled to the PEI and the PECs were used for affinity precipitation of lactate dehydrogenase (LDH) in beef heart extracts. The affinity precipitation was induced by a shift in FH, while the desorption and separation of LDH from the PECs was performed by addition of KCl combined with a shift in pH. LDH was obtained with a yield of 85% and a purification factor of approx. 11-fold. The polymers were recovered and reused once and the results became similar. Prior to the affinity precipitation, interfering nucleic acids were removed by precipitation with PEI. Copyright (C) 1996 Elsevier Science B.V.