GEMMI - GEneral MacroMolecular I/O

Gemmi is a library developed primarily for use in macromolecular crystallography (MX) programs.

Parts of the library may also be useful in structural bioinformatics (for symmetry-aware analysis of protein models), and in other molecular-structure sciences that use CIF files (as we have the fastest open-source CIF parser).

Gemmi is open-source (MPL), portable (Linux, Windows, MacOS), and fast. It is written in C++11, with Python (2 and 3) bindings, as well as with (soon-to-be-added) C and Fortran 2003 interface and (possibly in the future) with a subset of functionality translated to JavaScript for web applications.

Gemmi is a joint project of Global Phasing Ltd and CCP4, started in 2017, aiming to:

  • enhance macromolecular refinement programs (Refmac and BUSTER),
  • replace the CCP4 Coordinate Library (MMDB),
  • improve support for PDBx/mmCIF files in the CCP4 and GPhL software suites.

More details will be added as the project progresses.

Source code repository:


As of 2018 the library is under intensive development and not everything is documented yet. Just ask questions.