Role of water structure on phase separation in polyelectrolyte-polyethyleneglycol based aqueous two phase systems

Abstract

Partitioning of proteins in aqueous two-phase system(ATPS)has emerged as one of the important downstream processing techneques in bioprocess technology.The phase separation behavior of polyelectrolyte-polythyleneglycol(PEG)based ATPS have been studied to elucidate the mechanism controlling phase behaivor.The effect of various inorganic salt additvies revealed the importants of water structure as a major factor controlling phase separation in these systems.Nitrate and pottassium(water structure breaking ions)elevated the binodial line while sulphate,phosphate and sodium(water structure making ions)depressed the binodial line in both polyacrylic acid-PEG as-well-as polyethylelimine-PEG based ATPS.The effect of increase in concentration of either of the constitunt ploymers in both systems(at constant salt concentration)alwayes to led a greater propensity towards phase separation.These results point to a mechanism in which salt-assited polymer- modified water structure inactions play a central role in phase separation in ATPS.