Influence of system and molecular parameters upon fractionation of intracellular proteins from Saccharomyces by aqueous two-phase partition.

The interaction of molecular characteristics of proteins with the physicochemical properties of PEG-phosphate aqueous two-phase systems has been studied. This has involved characterization of protein molecular weight, charge, and hydrophobicity and study of PEG molecular weight and concentration, phosphate concentration, and pH. System characterization has been conducted in the context of limited stage fractionation procedures for protein recovery from baker's yeast. Results are presented which show that the degree of purification achieved is dependent on macromolecular surface properties rather than system operating conditions. A simple conceptual model of partitioning in PEG-phosphate aqueous two-phase systems is presented which is applicable in the rational design of fractionation procedures and serves to limit the amount of empirical experimentation necessary for the establishment of practical operations.