Estimation of binding constants of receptors and ligands by affinity capillary electrophoresis

An estimation method for determination of binding constants of receptors to ligands by affinity capillary electrophoresis was evaluated. On the basis of the theories of pseudostationary phase or so-called dynamic stationary phase, the retention factor (k) was used to represent the interaction between the receptor and ligand. k could be easily deduced from the migration times of the ligand and the receptor. Then, with the linear relationship of k versus the concentration of ligand in the running buffer, the binding constant K(b) was calculated from the slope and intercept. In order to test its feasibility, the calculation method was demonstrated using three model systems: the interactions between vancomycin and N-acetyl-D-Ala-D-Ala, ristocetin and N-acetyl-D-Ala-D-Ala, and carbonic anhydrase B and an arylsulfonamide. Estimated binding constants were compared with those determined by other techniques. The results showed that this estimation method was reliable. This calculation method offers a simple and easy approach to estimating binding constants of ligands to receptors.