LAUSR

MOTIVATION No rigorous statistical tests for detecting point-group symmetry in 3D charge density maps obtained by electron microscopy and related techniques have been developed. RESULTS We propose a method for determining the point-group symmetry of 3D charge density maps obtained by electron microscopy (EM) and related techniques. Our ab initio algorithm does not depend on atomic coordinates but utilizes the density map directly. We validate the approach for a range of publicly available single-particle cryo-EM data sets. In straightforward cases, our method enables fully automated single-particle 3D reconstruction without having to input an arbitrarily selected point-group symmetry. When pseudo-symmetry is present, our method provides statistics quantifying the degree to which the 3D density agrees with the different point-groups tested. AVAILABILITY AND IMPLEMENTATION The software is freely available at https://github.com/hael/SIMPLE3.0.