3D-Strudel - a novel model-dependent map-feature validation method for high-resolution cryo-EM structures

Recent technological advances in electron cryo-microscopy (cryo-EM) have led to significant improvements in the resolution of many single-particle reconstructions and a sharp increase in the number of entries released in the Electron Microscopy Data Bank (EMDB) every year, which in turn has opened new possibilities for data mining. Here we present a resolution-dependent library of rotamer-specific amino-acid map motifs mined from entries in the EMDB archive with reported resolution between 2.0 and 4.0[A]. We further describe 3D-Strudel, a method for map/model validation based on these libraries. 3D-Strudel calculates linear correlation coefficients between the map values of a map-motif from the library and the experimental map values around a target residue. We also present "Strudel Score", a plug-in for ChimeraX, as a user-friendly tool for visualisation of 3D-Strudel validation results.