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bioRxiv · 10.1101/722991

Measurement of Atom Resolvability in CryoEM Maps with Q-scores

Pintilie, G.·Zhang, K.·Su, Z.·Li, S.·Schmid, M. F.·Chiu, W.
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Abstract

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.

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Pintilie, G., Zhang, K., Su, Z., Li, S., Schmid, M. F., Chiu, W.. 2019-08-02. Measurement of Atom Resolvability in CryoEM Maps with Q-scores. https://doi.org/10.1101/722991

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