RELION (for REgularised LIkelihood OptimisatioN, pronounce rely-on) is a stand-alone computer program that employs an empirical Bayesian approach to refinement of (multiple) 3D reconstructions or 2D class averages in electron cryo-microscopy (cryo-EM). It is developed in the group of Sjors Scheres at the MRC Laboratory of Molecular Biology. Briefly, the ill-posed problem of 3D-reconstruction is regularised by incorporating prior knowledge: the fact that macromolecular structures are smooth, i.e. they have limited power in the Fourier domain. In the corresponding Bayesian framework, many parameters of a statistical model are learned from the data, which leads to objective and high-quality results without the need for user expertise. The underlying theory is given in Scheres (2012) JMB. A more detailed description of its implementation is given in Scheres (2012) JSB.
As the resolution revolution in cryo-EM progresses, many new software solutions are appearing for which the source code is closed and/or which are not free to use for everyone. The development of RELION is supported through long-term funding by the UK Medical Research Council, and we are proud to distribute RELION under a GPLv2 license. This means that anyone (including commercial users) can download, use and modify RELION without having to pay us anything. If RELION is useful in your work, please do cite our papers about it.
For examples of how we have used RELION, and for a complete list of publications about it, please see our web site.
- Download & install (also see the list of Known_issues and the Release notes)
- Conventions & File formats
- Tutorial (v2.1) (The quickest way to learning RELION-2.1)
- Tutorial (v3.0) (The quickest way to learning RELION-3.0-beta)
- Benchmarks & computer hardware (and how to use GPUs)
- FAQs (for useful tricks and in case of trouble)
If you have a question, please check the FAQs and whether the topic has been addressed already on the CCP-EM mailing list. If not, use the CCP-EM list to send us your message. Please, do not send us direct e-mails with general questions about RELION.