Chemical Component Dictionary

The Chemical Component Dictionary (formerly the HET Group Dictionary) is as an external reference file describing all residue and small molecule components found in PDB entries. This dictionary contains detailed chemical descriptions for standard and modified amino acids/nucleotides, small molecule ligands, and solvent molecules. Each chemical definition includes descriptions of chemical properties such as stereochemical assignments, aromatic bond assignments, idealized coordinates, chemical descriptors (SMILES & InChI), and systematic chemical names.

The chemical component dictionary is organized by the 3-character alphanumeric code that PDB assigns to each chemical component. New chemical component definitions appear in the dictionary as the entries in which they are observed are released in the PDB archive; consequently, the dictionary is updated with each weekly PDB release.