Moment Analysis of Affinity Kinetics in Inclusion Complex System between Thymol and Sulfated-β-cyclodextrin by Chromatographic Capillary Electrophoresis (CCE)

We developed a capillary electrophoretic (CE) method for the kinetic study of intermolecular interactions. Neither immobilization nor chemical modification, e.g., fluorescence labelling, of solute and ligand molecules is required. A concept of chromatographic capillary electrophoresis (CCE) was introduced as an experimental CE procedure. In the CCE mode, the migration of solute ligand complex in a capillary is stopped. Only solute molecules migrate and are detected. New moment equations were developed, which were essential for determining association and dissociation rate constants from elution peak profiles measured under the CCE conditions. The combination of the CCE concept and the moment theory leads to the CE method, i.e., moment analysis by CCE (MACCE). However, because it was hard to really perform CE experiments under the CCE conditions, we also developed practical experimental and data analysis procedures for the MACCE measurement. The reaction rate constants were analytically determined by the MACCE method for the formation and dissociation of the inclusion complex between thymol and sulfated-beta-cyclodextrin. It is unnecessary to fit elution curves numerically calculated to those experimentally measured for determining the rate constants. It was demonstrated that the MACCE method was effective for the kinetic study of intermolecular interactions.