Scheme 1.

Enrichment of DNA-linked ligands by crosslinking to a target protein. All library members contain the same 20-mer ssDNA sequence tethered to the unique dsDNA (ligand-encoding) construct. This allows a reactive group-ssDNA to be added by DNA hybridization after library synthesis and binding to a protein target. Following crosslinking, proteins can be denatured without impairing DNA hybridization and immobilized onto a solid support via an affinity tag (e.g. biotin). Stringent washing conditions can then be applied to remove non-ligands and maximize the enrichment of ligands.