Counter-current distributions of renin substrate and serum proteins in polyethylene glycol-salt systems

Abstract

Aqueous two-phase partitioning systems for proteins were prepared from polyethylene glycols and inorganic salt solutions. The effects of the molecular-weight range of the glycol, relative proportion of water, pH, temperature and nature of the inorganic cations and anions on the total solubilities and relative phase distributions of albumin, γ-globulin, total serum proteins and renin substrate were determined. These results led to the formulation of Na2SO4, (NH4)SO4 and Li4SO4 systems that were practical for counter-current distributions of renin substrate and unfractionated serum. Preliminary to the distribution of renin substrate, purification by batchwise partitioning was used. Substrate purities as high as 24300 Goldblatt units/g of protein were obtained. Serum was resolved into several groups of proteins, including γ-globulins with widely differing K values.