Characterizing a drug's primary binding site on albumin.

Surface plasmon resonance-based biosensors can be used to directly measure the binding of small molecules to albumin. We studied 12 drugs with different molecular masses and affinities for albumin to illustrate the benefits of the technology. To examine both high- and low-affinity sites on the protein, each drug was assayed across a 10,000-fold concentration range. The affinity constants determined from the biosensor assay corresponded with affinities determined by other methods. We expanded the utility of the biosensor technology by developing protocols to characterize drug displacement from albumin. Finally, we also compared how a representative panel of drugs bound albumins from 14 species. The results illustrate how biosensors can provide detailed information about the identification and affinity of a drug's primary binding site on albumin.