PT  - JOURNAL ARTICLE
AU  - Pintilie, Grigore
AU  - Zhang, Kaiming
AU  - Su, Zhaoming
AU  - Li, Shanshan
AU  - Schmid, Michael F.
AU  - Chiu, Wah
TI  - Measurement of Atom Resolvability in CryoEM Maps with Q-scores
AID  - 10.1101/722991
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 722991
4099  - http://biorxiv.org/content/early/2019/08/05/722991.short
4100  - http://biorxiv.org/content/early/2019/08/05/722991.full
AB  - CryoEM density maps are now at the point where resolvability of individual atoms can be achieved. However, resolvability is not necessarily uniform throughout the map. We introduce a quantitative parameter to characterize the resolvability of individual atoms in cryoEM maps, the map Q-score. Q-scores can be calculated for atoms in proteins, nucleic acids, water, ligands, and other solvent atoms, using models fitted to or derived from cryoEM maps. Q-scores can also be averaged to represent larger features such as entire residues and nucleotides. Averaged over entire models, Q-scores correlate very well with the estimated resolution of cryoEM maps for both protein and RNA. Assuming the models they are calculated from are well-fitted to the map, Q-scores can thus be used as another measure to indicate resolvability of features in cryoEM maps at various scales, from entire complexes down to individual atoms. Q-score analysis of multiple cryoEM maps of the same proteins derived from different labs confirms reproducibility of structural features down to water and ion atoms.