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-or-~-mannopyranoside and 4-nitrophenyl-N-acetyl-~-~-glucosaminide, in aqueous dextran-poly(ethy1ene 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 CH, 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.

pH dependence of the relative hydrophobicity and lipophilicity of amino acids and peptides measured by aqueous two‐phase and octanol–buffer partitioning

“…It has been shown previously (6) that the solvent features of two phases in aqueous two‐phase systems are different. This difference may be quantified by partitioning of a homologous series of monofunctional aliphatic compounds, such as dinitrophenyl‐(DNP‐) derivatives of amino acids (Gly, Ala, nor‐Val, nor‐Leu, and α‐amino‐n‐caprylic acid) as described previously in detail (7,9,11). Analysis of partitioning of such a series of compounds yields a linear relationship described by ln K = A + E * N C , where N C is the number of carbon atoms in the aliphatic alkyl chain of the partitioned solute molecule, and provides experimental values of an average ln K increment per CH 2 group ( E ) and of the total contribution of a polar moiety of the solute molecule ( A ).…”

“…6) that partitioning of a solute in an aqueous polymer two‐phase system is governed by the difference between the intensities of the solute–solvent interactions in the two phases. The partition coefficient of a solute in such a system represents the free energy of transfer of the solute between two aqueous media of different solvent properties, and hence it may be used as a measure of the relative hydrophobicity of the solute (6–9,11).…”

“…has been defined as the equivalent quantity of methylene units and suggested (6–8) to be used as a measure of the relative hydrophobicity of a solute (or a moiety). A positive value of N (CH 2 ) means that a given solute is hydrophobic and its relative hydophobicity is equal to that of N units of methylene groups.…”

“…This limitation is eliminated by using aqueous two‐phase partitioning (6–9). Aqueous two‐phase systems are widely used for separation and analysis of biological cells, proteins, nucleic acids, etc.…”

Use of the Aqueous Two-Phase Partition Technique for Characterization and Quality Control of Recombinant Proteins

“…12,13 Numerous similarities between fundamentals of solute partitioning in aqueous polymer two-phase systems and in common solvent systems, such as the octanol-water system, have been found. 6 It has been established by Zaslavsky et al, [14][15][16] in particular, that the logarithm of the partition coefficient ofa solute in aqueous Dextran-poly(ethylene glycol) and Dextran-Ficoll two-phase systems is a measure of the solute relative hydrophobicity. The hydrophobicity of a solute is definedI' as a measure of the intensity of molecular interactions of the solute with water in dispersed systems, the dispersing medium in which is water.…”