Acta Crystallographica Section D

Q-scores are calculated for atomic models derived from 3D electron microscopy maps, measure how well the model fits the map and reflect the quality of the map itself. Here, we develop a statistical model for Q-scores applied to many maps and models in the EMDB and PDB, respectively, and show how it can be used to assess the reliability of entire models as well as their subcomponents.

In the context of cryo-EM reconstruction, we provide a theoretical analysis showing that the condition number of the optimization problem is particularly large at high resolution, leading to slow convergence of gradient-based methods such as stochastic gradient descent. We then propose a method to overcome this issue by computing a preconditioner using Hutchinson's estimator, which results in improved convergence speed, as evidenced by numerical experiments.

A method for multi-crystal data collection and the software programs Dozor, Dozor-m2 and Resheteau for the detection of individual crystals, the determination of their positions on a sample holder and the estimation of their dimensions and shapes based on double raster X-ray scans are presented.