Assessing Data Quality


The first step after data processing is analysis of the diffraction data to assess quality and detect any pathologies that might make structure solution difficult. Data quality can be quantified in terms of resolution of diffraction, anomalous signal-to-noise, and consistency with prior knowledge about diffraction from crystals.

Possible pathologies include twinning, translational non-crystallographic symmetry, anisotropy, and missed symmetry elements. For example, crystals are considered ‘twinned’ if two or more separate crystals (domains) are intergrown in such a way that they share some crystal lattice points in a symmetrical manner. And translational noncrystallographic symmetry (tNCS) occurs when two or more independent copies of a molecule or assembly have a similar orientation in the asymmetric unit of the crystal.


In Phenix, the phenix.xtriage program analyzes data to assess quality and detect possible problems. For most uses, the program only requires a reflection file containing the data set you wish to analyze. Running phenix.xtriage generates information about the data set, which is best viewed in the GUI as graphs and tables. The first section of the output provides an overall assessment of the data.

How to use the phenix.xtriage GUI: Click here

Common issues

Related programs and Documentation

Phenix reference manual for phenix.xtriage