The binding response at equilibrium provides a direct measure of the amount of complex formed in the presence of free material. The top figure represents binding responses for warfarin (from 400 to 0.1 mM) interacting with immobilized human albumin.

In order to extract a binding constant, the responses at equilibrium were plotted verses the injected warfarin concentration. These data were fit to a two-independent-sites binding model. The affinity for site 1 and site 2 were determined to be ~2 and ~250 mM, respectively. These results are consistent with the known warfarin binding properties of albumin.

For more information on measuring drug/albumin interactions using Biacore see:
Rich et al., 2001 Anal Biochem 296: 197-207
Day and Myszka, 2003 J Pharm Sci 92:333-343.