Open AccessIntensity statistics in twinned crystals with examples from the PDB
Author(s) -
Lebedev Andrey A.,
Vagin Alexei A.,
Murshudov Garib N.
Publication year - 2006
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444905036759
Subject(s) - crystal twinning , macle , materials science , crystallography , computer science , statistics , mathematics , chemistry , microstructure
Entries deposited in the Protein Data Bank as of February 2004 for which both model and X‐ray data were available were analysed to identify cases of twinning using such simple statistics as the R factor between potential twin‐related reflections. Careful consideration of all identified twins showed that in many cases twinning was ignored during structure solution and refinement. Manual analysis of the models showed that twinning often occurs in association with rotational pseudosymmetry parallel to the twinning operator. The coexistence of these two phenomena complicates the detection and diagnostics of twinning using currently available twinning tests. It was concluded that a twinning‐detection step should be incorporated in every stage of structure analysis from data acquisition to refinement and validation.