HYDROPHOBIC PARTITIONING OF PROTEINS IN A 2-PHASE AQUEOUS SYSTEM OF POLY(OXYETHYLENE)-DEXTRAN ALTERNATIVELY DERIVATIZED BY 2-HYDROXY-3-PHENOXYPROPYL GROUP

We have observed that in a two-phase aqueous system composed of poly(oxyethylene) and dextran, trypsin, ovalbumin, serum albumin and immunoglobulin G are preferentially partitioned into the dextran phase. The accumulation of proteins in this more hydrophilic phase increased with the increasing concentration of the polymers in both phases. This trend remained essentially unchanged even after the hydrophobization of the poly(oxyethylene) (POE) phase by 2-hydroxy-3-phenoxypropyl (HPP). The affinity of all four proteins for the dextran phase decreased after the hydrophobization of the dextran phase by the HPP ligand. The affinity decrease was uniform with all four proteins. The hydrophobic partitioning of all four proteins in the systems composed of (HPP-POE) and dextran and of POE and (HPP-dextran) was probably governed by an identical mechanism. The size and charge of the globular protein played an important role in this mechanism.