Chemical component search
The Chemical Component Dictionary gives detailed chemical descriptions of all residue and small molecule components found in PDB entries including standard and modified amino acids/nucleotides, small molecule ligands and solvent molecules.
27268 chemical components - 25611 as free ligands in 112650 PDB files - 2021 as non-standard polymeric components in 25707 PDB files
Ligand Expo is another browser for the Chemical Component Dictionary and supports searches for current and obsolete chemical components.