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The partition behavior or proteins in an aqueous two-phase system of poly (ethyleneglycol)-potassium phosphate buffer (PEG/PPB) was investigated. The proteins of different surface hydrophobicity, i.e. Bovine serum albumin (BSA), β-lactoglobulin, ovalbumin. moved to the PPB-rich bottom phase in a PEG (12%)/PPB (12%) two-phase system resulting in very low partition coefficients. When the concentration of PPB increased to 15% level, the electric potential of bottom phase changed from+50 ㎷ to zero and the partition coefficient tended to increase. The change in the molar ratio of K₂HPO₄/KH₂PO₄ in PPB from 1.43 to 9.55 caused the volume ratio of top to bottom phase (V_t/V_b) to he decreased and protein partition coefficient increased. When the concentration of PPB was elevated from 14% to 26%, the V_t/V_b decreased from 1.5 to 0.39 and the partition coefficient of proteins increased drastically; β-lactoglobulin 74 fold, BSA 32 fold, ovalbumin 12 fold and lysozyme 5 fold.
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