Partition of Proteins in a Three‐Phase System

A system consisting of three liquid phases has been used for partition of proteins. It is composed of water and three high‐molecular compounds: dextran, Ficoll and poly(ethyleneglycol) the latter partly converted into a derivative. All the three phases have a high water content, 71–79%, and dissolve proteins. Hemoglobin, serum albumin, lysozyme and hexokinase, as well as yeast lysate, have been partitioned in the system. The distribution of some glycolytic enzymes present in the lysate has been determined. At low pH, the proteins are found in the bottom phase. With increasing pH the affinity successively increases first for the middle phase and then for the top phase. The pH at which accumulation in the middle phase occurs is specific for each protein. Under certain conditions different isoenzymic forms can be separated by a single partition step. Practical applications of the three‐phase system are suggested.