Crystallographic and thermodynamic comparison of structurally diverse molecules binding to streptavidin

Crystallographic structures and thermodynamic binding parameters are compared for three structural classes of streptavidin ligand including d-biotin, 2-[(4'-hydroxyphenyl)-azo] benzoate and the peptide NH₂-Phe-Ser-His-Pro-Gln-Asn-Thr-COOH. Descriptions of these structural and thermodynamic observations emphasize the diversity of potential strategies for improving ligand affinity.