Crystallographic model quality at a glance
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Updated: Jun 25, 2026

On-Chip Crystallization and Large-Scale Serial Diffraction at Room Temperature
Published on: March 11, 2022
Ludmila Urzhumtseva1, Pavel V Afonine, Paul D Adams
1Architecture et Réactivité de l'ARN, Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire, CNRS, Strasbourg, France.
Abstract:
A crystallographic macromolecular model is typically characterized by a list of quality criteria, such as R factors, deviations from ideal stereochemistry and average B factors, which are usually provided as tables in publications or in structural databases. In order to facilitate a quick model-quality evaluation, a graphical representation is proposed. Each key parameter such as R factor or bond-length deviation from ;ideal values' is shown graphically as a point on a ;ruler'. These rulers are plotted as a set of lines with the same origin, forming a hub and spokes. Different parts of the rulers are coloured differently to reflect the frequency (red for a low frequency, blue for a high frequency) with which the corresponding values are observed in a reference set of structures determined previously. The points for a given model marked on these lines are connected to form a polygon. A polygon that is strongly compressed or dilated along some axes reveals unusually low or high values of the corresponding characteristics. Polygon vertices in ;red zones' indicate parameters which lie outside typical values.
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