LAUSR

The availability of reliable methods for the characterization of the binding of small molecule ligands to protein targets is crucially im-portant for Drug Discovery. We have adapted a method, routinely used for the characterization of monoclonal antibodies (Enzyme-linked immunosorbent assay, or "ELISA"), to small molecule ligands, using fluorescein conjugates and anti-fluorescein antibodies as de-tection reagents. The new small molecule-ELISA methodology was tested using a panel of binders specific to carbonic anhydrase II, with dissociation constants ranging between 6 μM and 14 nM. An excellent agreement was found between ELISA measurements and fluo-rescence polarization results. The methodology was also extended to BIAcore measurements and implemented for ligands coupled to oligonucleotides. Small molecule-ELISA procedures are particularly useful in the context of DNA-encoded libraries, for which hit valida-tion procedures need to be performed on dozens of candidate molecules and hit compounds can be conveniently resynthesized on DNA.