One of the eight atom classes used to describe atoms in LPC: - I = 'Hydrophilic' - II = 'Acceptor' - III = 'Donor' - IV = 'Hydrophobic' - V = 'Aromatic' - VI = 'Neutral' - VII = 'Neutral-donor' - VIII = 'Neutral-acceptor' String of length 8 which uniquely identifies a ligand from a PDB file. It consists in the concatenation of the "Residue Name" (*), of the "Chain Identifier" (*) and of the "Residue Sequence Number" (*). (*) see PDB format, HETATM field. Single character which identifies the residue type. It is limited to the 20 usual residue one-letter codes, and to 'X' which stands for anything else. 3-letter string which identifies the residue type. It is not restricted to a predefined list of three-letter codes, so as to allow for unusual residue types (i.e. 'HSE', or 'GLX'). String of length 4, starting with a number between 1 and 9 (both inclusive), followed by three alphanumeric characters.