Abstract
Here, we describe the third major release of RELION. CPU-based vector acceleration has been added in addition to GPU support, which provides flexibility in use of resources and avoids memory limitations. Reference-free autopicking with Laplacian-of-Gaussian filtering and execution of jobs from python allows non-interactive processing during acquisition, including 2D-classification, de novo model generation and 3D-classification. Per-particle refinement of CTF parameters and correction of estimated beam tilt provides higher resolution reconstructions when particles are at different heights in the ice, and/or coma-free alignment has not been optimal. Ewald sphere curvature correction improves resolution for large particles. We illustrate these developments with publicly available data sets: together with a Bayesian approach to beam-induced motion correction it leads to resolution improvements of 0.2-0.7 Å compared to previous RELION versions.
Highlights
Macromolecular structure determination by single-particle analysis of electron cryo-microscopy images has undergone rapid progress in recent years
The functions that perform the expectation step in RELION-3 can use the same code path and structure as the graphical procesing units (GPUs)-accelerated code that was introduced in RELION-2, even if executing on systems without GPUs
The new functionality in RELION-3 allows faster, more automated and higher resolution cryo-EM structure determination compared to previous versions
Summary
Macromolecular structure determination by single-particle analysis of electron cryo-microscopy (cryo-EM) images has undergone rapid progress in recent years. Before 2010, cryo-EM structures to resolutions beyond 4 Ahad only been obtained for large icosahedral viruses, for example Jiang et al, 2008, Yu et al, 2008, and Zhang et al, 2008. In 2012, the availability of the first prototypes of direct electron detectors, which recorded images with unprecedented signal-to-noise ratios (McMullan et al, 2009), represented a crucial step forward. This advance was closely followed and partially overlapped with important improvements in image processing software. They led to what was termed the ’resolution revolution’ in cryo-EM structure determination (Kuhlbrandt, 2014)
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