Acrylamide derivatives of starch in two-phase systems used to purify proteins. Part I. Synthesis, properties and phase diagrams

Binary polymer mixtures, forming two-phase aqueous systems, were studied. One component (P) was either polyoxyethylene glycol (PEG 10 000) or vinylimidazole/vinylcaprolactam copolymer (VI/VCL); the other component (Q) was an acrylamide starch derivative (APS) or a commercial dextran (Dextran T70) which was used as a standard polymer. The VI/VCL copolymers had varying compositions (Table 2) and the APS had varying acrylamide contents (Table 1). Phase diagrams were determined for a series of P-Q mixtures (Figs. 2-9) and the P and Q content ranges were established at which two-phase systems were formed. With aqueous 0.5% NaCl added, the composition ranges were found to have narrowed. The growth of hydrophilic VI/VCL copolymers caused by increased content of VI was found to render a two-phase system difficult or even impossible to form (Figs. 8, 9). The APS were found to present efficient substitutes for expensive dextran and they can be used as two-phase system components to purify proteins.