Open AccessMIR phasing using merohedrally twinned crystals
Author(s) -
Terwisscha van Scheltinga Anke C.,
Valegård Karin,
Hajdu Janos,
Andersson Inger
Publication year - 2003
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s090744490302122x
Subject(s) - crystal twinning , phaser , fraction (chemistry) , materials science , crystallography , atom (system on chip) , crystal (programming language) , macle , crystal structure , computer science , chemistry , physics , microstructure , optics , programming language , organic chemistry , embedded system
Merohedral twinning is a crystal‐growth disorder that seriously hinders the determination of macromolecular crystal structures by isomorphous replacement. The strategies used in the structures solved so far are discussed. Several methods can be used to determine the extent of twinning, the twin fraction and to detwin the data. Accurate determination of the twin fraction by analysing heavy‐atom refinement statistics is possible, but only influences the resulting phases slightly. It seems more crucial to restrict the variation in twin fractions between data sets, either by making the twin fractions of some data sets artificially higher or by screening crystals to obtain data with a low twin fraction.