Comparison between binding analyses performed by equilibrium dialysis and partitioning in aqueous two-phase systems exemplified by the binding of cibacron blue to serum albumin

Abstract

Partitioning in two-phase systems was used as a separation method in binding analyses and compared with equilibrium dialysis. A phase system was chosen to give partitioning conditions with the reactants in different phases. The interaction between serum albumin and Cibacron Blue F3G-A was used as a model system. The protein partitioned to the bottom phase and the ligand to the top phase in a phase system consisting of poly(ethylene glycol) and dextran. When both albumin and Cibacron Blue were present in the phase system, the degree of binding was observed as a translocation of ligand from the top to the bottom phase. An evaluation method that compensates for the amount of free reactant in the phase with the binding protein is presented.