Binding constant determination of drugs toward subdomain IIIA of human serum albumin by near-infrared dye-displacement capillary electrophoresis

Drug binding to serum albumin influences several important pharmacological properties such as toxicity, solubility, activity, distribution, and excret ion. It is therefore of interest to have methodologies that allow for the d etermination of drug-albumin affinity constants while simultaneously provid ing information on the location of the drug binding site. In the present wo rk we describe a method for the determination of binding constants of drugs known to bind to subdomain IIIA of serum albumin. Drugs used in the study were ketoprofen, ibuprofen, quinidine, naproxen, imipramine, and clofibrate . Binding constants of the drugs were determined by near-infrared dye-displ acement capillary electrophoresis. The dye-displacement technique uses a co mpetitive-type interaction between the drug of interest and a dye probe to arrive at a binding constant. A heptamethine cyanine dye was used as a prob e for drug binding at subdomain IIIA of serum albumin. The utility of the d ye as a noncovalent label for serum albumin was investigated. Additionally, the ability of the method to illustrate enantioselective binding is shown. The dye displacement technique has advantages over current electrophoresis -based techniques in that it is faster and uses less reagent.