Partition of Proteins in Two‐Phase Systems Containing Charged Poly(ethylene glycol)

Abstract

Proteins have been partitioned in dextran–poly(ethylene glycol)–water biphasic systems containing positively charged poly(ethylene glycol). The effect of pH, buffer concentration, polymer concentration, protein concentration and temperature on the partition has been investigated. Characteristic extraction profiles are obtained when the percentage of protein in the upper phase is plotted versus pH. By keeping the salt concentration low, very steep extraction profiles can be obtained. Thus, within an interval of one pH unit, a protein is transferred from one phase to the other. This pH‐interval is located close to the isoelectric point of the protein. The possibility of resolving the components in a natural enzyme mixture, yeast lysate, by counter‐current distribution in this type of biphasic system has been investigated. According to activity measurements, several glycolytic enzymes are resolved by this procedure. Good separation is achieved. For some of the enzymes the activity is split into more than one peak in the counter‐current distribution.