Take a closer look: Unexpectedly, a pair of enantiomeric ligands proved to have similar binding affinities for acetylcholinesterase. Further studies indicated that the enantiomers exhibit different thermodynamic profiles. Analyses of the noncovalent interactions in the protein-ligand complexes revealed that these differences are partly due to nonclassical hydrogen bonds between the ligands and aromatic side chains of the protein.
        
Representative scheme of ACHE structure and an image from PDBsum server
Databases
PDB-Sum
4ARA Previously Class, Architecture, Topology and Homologous superfamily - PDB-Sum server
FSSP
4ARAFold classification based on Structure-Structure alignment of Proteins - FSSP server