title: Helical reconstruction in RELION.
abstract: We describe a new implementation for the reconstruction of helical assemblies in the empirical Bayesian framework of RELION. Our approach calculates optimal linear filters for the 3D reconstruction by embedding helical symmetry operators in Fourier-space, and deals with deviations from perfect helical symmetry through Gaussian-shaped priors on the orientations of individual segments. By incorporating our approach into the standard pipeline for single-particle analysis in RELION, our implementation aims to be easily accessible for non-experienced users. Although our implementation does not solve the problem that grossly incorrect structures can be obtained when the wrong helical symmetry is imposed, we show for four different test cases that it is capable of reconstructing structures to near-atomic resolution.
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH Cambridge, UK.
authors.forename: Shaoda
authors.initials: S
authors.lastname: He
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH Cambridge, UK. Electronic address: scheres@mrc-lmb.cam.ac.uk.
authors.forename: Sjors H W
authors.initials: SHW
authors.lastname: Scheres
mesh_terms: D000465:Algorithms; D001499:Bayes Theorem; D030562:Databases, Protein; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional
keywords: Cryo-electron microscopy; Helical symmetry; Image processing; Regularised likelihood optimisation; Single-particle analysis