Small Molecule Structures

The largest collection of small molecule experimental structures is the Cambridge Structural Database (CSD).  These experimental structures from the scientific literature have been checked for errors by the Cambridge Crystallographic Data Center (CCDC).  Unfortunately, they are not available for direct download on the Internet.  CrystMol can import structure information from text files written in the CSD .cif and the CSD .dat format.  For more information about obtaining and using the CSD, visit the CCDC Web site . (http://www.ccdc.cam.ac.uk/)

A large number of accurate experimental crystal structures are published in the scientific journal, Acta Crystallographia, especially in Acta Cryst., Section C.  Acta Cryst. is published by the International Union of Crystallography (IUCr). The IUCr Web site (http://www.iucr.ac.uk/) supports downloading structural information in text files written in the Crystallographic Information File (CIF) format.  CrystMol can import structural information from CIF format files.

Macromolecular Structures

The largest collection of macromolecular structures is the Protein Data Bank (PDB).  Structures are available for a very large number of proteins and nucleic acids.  Files may be downloaded from the PDB Web site (http://www.rcsb.org/pdb/) in two formats, the older PDB format, and the newer macromolecular CIF format (mmCIF).  CrystMol can import structural information from text files written in the PDB or mmCIF formats.

Keyboard Entry of Structures

CrystMol can also import structure information written in the CRYM format--an obsolete older column-oriented format. If you need to work with structural information not available in computer readable form, the CRYM format offers an easy way of entering both Cartesian coordinate structures and crystal structures. Details on the CRYM format are given in the CrystMol Reference Manual.