Partitioning of vancomycin using poly(ethylene glycol)-coupled ligands in aqueous two-phase systems

Affinity partitioning describes a process in which a biospecific ligand is used to manipulate the partitioning behavior of a biomolecule by coupling a ligand to one of the phase-forming polymers. It combines the high selectivity of affinity chromatography with the scalability of aqueous two-phase extractions. Fundamental studies have been made on the factors affecting affinity partitioning of the antibiotic vancomycin using a series of polymer-ligands composed of the D-Ala-D-Ala peptide coupled to poly(ethylene glycol) in methoxypoly(ethylene glycol)/dextran aqueous two-phase systems. The effects of varying the ligand molecular weight, the ligand binding interaction, the number of binding sites, the tie-line length, and the aggregation of vancomycin have been measured. A modification of the Flanagan and Barondes model for affinity partitioning has been suggested to explain the results. The modified model accounts for the changes in the surface properties of the biomaterial on complex formation.