Structures of nuclear retinoic acid receptors in the absence of ligand (left), binding the agonist 9-cis- retinoic acid (middle) or the antagonist BMS6I4 (right) in the ligand binding pocket (LBP)

The smaller the Kd is the greater the affinity of the drug for the receptor.

Captopril as example of a charge-charge interaction with the ACE receptor.

Zaleplon as example of ion-dipole and dipole-dipole interactions

Crystal structure of a short peptide L-Lys-D-Ala-D- Ala (bacterial cell wall precursor [in green]) bound to the antibiotic vancomycin (in blue) through five hydrogen bonds