Partitioning in aqueous two-phase systems as a method of estimation of the relative hydrophobicity of solutes

Abstract

Partitioning of two non-ionic glycosides, 4-nitrophenyl-α-D-mannopyranoside and 4-nitrophenyl-N-acetyl-β-D-glucosaminide, in aqueous dextran–poly(ethylene glycol) and dextran–polyvinylpyrrolidone two-phase systems of different polymer concentrations and various ionic compositions has been studied. The differences in the abilities of the aqueous media in the coexisting phases of the systems used to participate in ionic and hydrophobic hydration interactions with a solute being partitioned have been estimated previously. The relative hydrophobicity of the solutes expressed in equivalent quantity of CH₂ groups depends on the composition of the aqueous medium (the nature and concentration of the salts present, the nature of the phase polymers). The difference between the relative hydrophobicities for the non-ionic solutes, however, is independent of the above factors. This indicates that the partition technique can be considered as an adequate general method for estimation of the relative hydrophobicity of solutes.