What is a .MMCIF file?
mmCIF is CIF syntax applied to proteins and nucleic acids. It replaced the fixed-column PDB format, which had run out of room - the old layout could not express a structure with more than 99,999 atoms or 62 chains.
- Did you know
- The Protein Data Bank made mmCIF its master format in 2014; the classic PDB file is now a lossy export of it.
- mmCIF extends the Crystallographic Information File, the broader IUCr standard for sharing crystal-structure data, to handle huge biological molecules.
- Since 2019 the Protein Data Bank has required new crystallographic depositions in PDBx/mmCIF, cementing its place over the legacy PDB layout.
- 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
- .MMCIF 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 .MMCIF file
- Drag a .MMCIF 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.