MIME types: chemical/x-cif, chemical/x-mmcif 3D molecular model file. Used in cheminformatics applications and on the web for storing and exchanging molecule models. Commonly used as an alternative to the PDB format. mmCIF is an acronym derived from Macromolecular Crystallographic Information File. Derived from the CIF file format. Plain text format. Stores structure information for large biological molecules such as proteins and nucleic acids. Developed between 1990 and 1997 by the International Union of Crystallography.