MIR phasing using merohedrally twinned crystals

A. C. Terwisscha van Scheltinga, K. Valegård, J. Hajdu, I. Andersson

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Abstract

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.
Original languageEnglish
Pages (from-to)2017-2022
Number of pages6
JournalActa Crystallographica Section D: Biological Crystallography
Volume59
DOIs
Publication statusPublished - Nov-2003

Keywords

  • MIR phasing
  • merohedral twinning
  • X-RAY
  • 1,5-BISPHOSPHATE CARBOXYLASE
  • ISOMORPHOUS REPLACEMENT
  • PROTEIN CRYSTALS
  • ACTIVE-SITE
  • RESOLUTION
  • DIFFRACTION
  • SYNTHASE
  • EUROPAEA
  • SPINACH

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