What is a .CIF file?
CIF is how a crystal structure is archived: not just atoms and coordinates but the unit cell, the symmetry operations that generate the rest of the crystal from them, and the experiment that produced it.
- Did you know
- CIF is a self-describing tag/value format designed to be read by both people and software, and it became the recommended way to submit a crystallography paper to Acta Crystallographica in 1992, the year after the standard was published.
- CIF is maintained by the International Union of Crystallography, and journals require it when publishing a newly solved crystal structure.
- A CIF is plain text of name-value pairs recording the unit-cell dimensions, symmetry and atomic positions that define a crystal.
- What Analyser reads
- Open chemical structures and see the molecule: MOL and SDF connection tables, MOL2, plain XYZ coordinates, Protein Data Bank entries and mmCIF/CIF crystallographic files, all drawn in an interactive 3D viewer you can rotate, zoom and restyle. Small molecules come up as ball-and-stick with the standard element colours; proteins and nucleic acids get a cartoon instead, drawing each chain as a ribbon along its backbone with helices and sheets picked out and any bound ligand still shown as sticks - which is the only way a structure of tens of thousands of atoms is readable at all. Alongside the picture, the composition is worked out from the atoms actually present rather than from any label in the file: molecular formula in Hill notation, molecular weight, net charge, element counts, and for a macromolecule the chain, residue and secondary-structure counts plus every non-polymer group - bound drugs, cofactors, metal ions and crystallisation buffer. PDB headers give up the entry ID, title, experimental method and resolution; an SDF is stepped through record by record with each molecule's tagged data fields read out.
- Depth of analysis
- .CIF is an identification-grade format: Analyser recognises it from its bytes and decodes the header metadata it carries, rather than opening it in a full viewer. Formats that do get a full viewer are marked "Full" on the formats page.
- Open a .CIF file
- Drag a .CIF file onto the Analyser home page (or tap to pick one). It is identified entirely in your browser - nothing is uploaded, there is no account, and it works offline once installed.