Estimation of high-order aberrations and anisotropic magnification from cryo-EM data sets in RELION-3.1

We present methods that detect three types of aberrations in single-particle cryo-EM data sets: symmetrical and antisymmetrical optical aberrations and magnification anisotropy. Because our methods only depend on the availability of a preliminary 3D reconstruction from the data, they can be used to correct for these aberrations for any given cryo-EM data set, a posteriori. Using five publicly available data sets, we show that considering these aberrations improves the resolution of the 3D reconstruction when the effects are present. The methods are implemented in version 3.1 of our open-source software package RELION.