atomic coordinate record containing the X,Y,Z orthogonal � coordinates for atoms in standard residues (amino acids and nucleic acids).

The DBREF record provides cross-reference links between PDB sequences (what appears in SEQRES record) and a corresponding database sequence.

atomic coordinate record containing the X,Y,Z orthogonal � coordinates for atoms in nonstandard residues. Nonstandard residues include inhibitors, cofactors, ions, and solvent. The only functional difference from ATOM records is that HETATM residues are by default not connected to other residues. Note that water residues should be in HETATM records.