Abstract
Conditions and the limits of measurement for protein-binding studies by the ultracentrifugation (UC) method were investigated, and the UC method was compared with the currently used equilibrium dialysis (ED) method in terms of accuracy and reliability. Serum albumin (SA) concentrations of around 5.0×10-5 M and drugs with molecular weights of less than 400 were suitable for the UC method. The optimal rotation speed was considered to be 30000 rpm (61380×g). The UC method and ED method were compared in measurements of the binding of 4'-hydroxyazobenzene-2-carboxylate, 2-naphthoate, salicylate and warfarin to bovine SA and human SA. The UC method was confirmed to be comparable with the ED method in terms of reliability and rather superior in terms of reproducibility, especially at low drug concentrations.
