information. REMARK records can contain free-form annotation, but they also accommodate standardized information; for example, the REMARK 350 BIOMT records describe how to compute the coordinates of the experimentally observed multimer from those of the explicitly specified ones of a single repeating unit. SEQRES records give the sequences of the three peptide chains (named A, B and C), which are very short in this example but usually span multiple lines. ATOM records describe the coordinates of the atoms that are part of the protein. For example, the first ATOM line above describes the alpha-N atom of the first residue of peptide chain A, which is a proline residue; the first three floating point numbers are its x, y and z coordinates and are in units of Ångströms. The next three columns are the occupancy, temperature factor, and the element name, respectively. HETATM records describe coordinates of hetero-atoms, that is those atoms which are not part of the protein molecule. Molecular visualization software capable of displaying PDB files 3d Animation software capable of displaying PDB files See also Chemical file format ScientificPython — provides an interface for Python Software for molecular mechanics modeling References External links PDB Format Guide This is the current version (3.3) of the PDB format specification. PDBML A more recent, alternative XML-based file format for molecular coordinates. The RCSB Protein Data Bank Protein Data Bank in Europe The Molecular Modeling DataBase (MMDB) from NCBI The wwPDB remediation Project from wwPDB MakeMultimer An online tool for expanding BIOMT records in PDB files Molecules iPad/iPhone App to display PDB files Python Macromolecular Library (mmLib) — a Python library capable of reading and writing PDB file formats Computational chemistry Chemical file formats Biological databases