RELION: implementation of a Bayesian approach to cryo-EM structure determination

J Struct Biol. 2012 Dec;180(3):519-30. doi: 10.1016/j.jsb.2012.09.006. Epub 2012 Sep 19.


RELION, for REgularized LIkelihood OptimizatioN, is an open-source computer program for the refinement of macromolecular structures by single-particle analysis of electron cryo-microscopy (cryo-EM) data. Whereas alternative approaches often rely on user expertise for the tuning of parameters, RELION uses a Bayesian approach to infer parameters of a statistical model from the data. This paper describes developments that reduce the computational costs of the underlying maximum a posteriori (MAP) algorithm, as well as statistical considerations that yield new insights into the accuracy with which the relative orientations of individual particles may be determined. A so-called gold-standard Fourier shell correlation (FSC) procedure to prevent overfitting is also described. The resulting implementation yields high-quality reconstructions and reliable resolution estimates with minimal user intervention and at acceptable computational costs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Bacteria / chemistry
  • Bacterial Proteins / chemistry*
  • Bayes Theorem
  • Cryoelectron Microscopy
  • Image Processing, Computer-Assisted*
  • Imaging, Three-Dimensional
  • Protein Conformation
  • Software*
  • Viral Proteins / chemistry*
  • Viruses / chemistry


  • Bacterial Proteins
  • Viral Proteins