Affinity partitioning: a new approach for studying dye-protein interactions.

Affinity partitioning in an aqueous two-phase system composed of dextran and dye-liganded polyethylene glycol was applied to the investigation of the affinity of phosphofructokinase and glucose-6-phosphate dehydrogenase from baker's yeast, as well as of albumin and prealbumin from human serum to diverse reactive dyes. From the change in the partition coefficient K of the proteins in the two-phase system in the presence and in the absence of the dye-liganded polymer, expressed as delta log K, quantitative data for the maximal extraction power and for the affinity of the proteins to various reactive dyes were obtained. The affinity partitioning effect on prealbumin is markedly increased by an excess of monomeric albumin. This points to an interaction of the two proteins in the presence of the dye, Remazol Yellow GGL. The competitive effect of various natural ligands on binding reactive dyes to proteins can be investigated by means of affinity phase partitioning as demonstrated on phosphofructokinase and prealbumin.