Stopped-flow studies on drug-protein binding. Analog-computer analysis of the pH-dependent binding kinetics of warfarin and human serum albumin.
Binding curves obtained by the stopped-flow method for the association of warfarin and human serum albumin (HSA) at pH 6.0 and 9.0 have been analysed with digital- and analog computers. The first association product (WHSA') at pH 6-9 does not contribute to the observed fluorescence enhancement during warfarin-HSA complex formation. A similar consecutive relaxation process leads to a more stable warfarin-HSA complex, with HSA in the neutral (N)-form (pH 6) and base (B)-form (pH 9). This rearrangement can be measured by stopped-flow (k 2 = 31 s-1 at pH 6; K'2 = 63 s-1 at pH 9). At pH 6 a further concentration dependent relaxation process has been observed indicating that the complex of warfarin with the N-form of HSA gets partially converted into its B-form with a half-time for this N leads to B transition in the range of 0.2-0.4 s. A drug such as warfarin can act as effector molecule for conformational changes of the HSA tertiary and quaternary structure during the formation of a high affinity complex.
D003202:Computers, Analog; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014859:Warfarin / Q000097:blood*
D004364:Pharmaceutical Preparations; D012709:Serum Albumin; D014859:Warfarin