DRUG-BINDING IN HUMAN-SERUM ALBUMIN AS ASSAYED BY DIAFILTRATION AND FLUORIMETRY

The binding of salicylate has been investigated by equilibrium ultrafiltration at various concentrations of human serum albumin up to 50 mg/ml. Very pronounced differences in the binding of the ligand at the different protein concentrations were observed, notably the amount bound per protein molecule decreased at constant levels of free (not total) salicylate, as the protein concentration was increased. A detailed investigation of the effect of the binding of the first molecules of salicylate to the protein by fluorescence indicated that the initial binding of salicylate was very tight indeed and a minor conformational change in the albumin allowing further molecules to be bound. This initial binding was also dependent on the protein concentration. © 1979.