Partition coefficients of amino acids, peptides, and enzymes in dextran + poly(ethylene glycol) + water aqueous two-phase systems

Partition coefficients are measured for five amino acids (aspartic acid, asparagine, methionine, cysteine and histidine) and two peptides (glycyl-glycine and hexa-glycine) in dextran + poly(ethylene glycol) + water aqueous two-phase system. The partition coefficients of the amino acids and peptides are correlated using the osmotic virial equation. The interaction coefficients contained in the equation can be calculated by hydrophilic group parameters. The partition coefficients of α-amylase calculated by the osmotic virial equation with the hydrophilic group parameters are in fairly good agreement with the experimental data, though a relatively large discrepancy is shown for β-amylase.