Tight-binding streptavidin ligands from a cyclic peptide library

During the screening of a soluble library of cyclo(AXXXXXAE)K---CONH2, a cyclic peptide cyclo(AHPQFPAE)K---CONH2 was identified as a tight-binding ligand (IC50 = 128 nM) and found to bind 1000-fold more tightly than its linear peptide to streptavidin. The results of this study suggest library screening of conformationally constrained cyclic peptides can be an effective means for the discovery of high affinity ligands.