Analysis and characterization of data from twinned crystals.

  title={Analysis and characterization of data from twinned crystals.},
  author={N Chandra and K. Ravi Acharya and Peter C. E. Moody},
  journal={Acta crystallographica. Section D, Biological crystallography},
  volume={55 Pt 10},
It is difficult but not impossible to determine a macromolecular structure using X-ray data obtained from twinned crystals, providing it is noticed and corrected. For perfectly twinned crystals, the structure can probably only be solved by molecular replacement. It is possible to detect and characterize twinning from an analysis of the intensity statistics and crystal packing density. Tables of likely twinning operators and some examples are discussed here. 

Figures and Tables from this paper

Molecular structure from X-ray diffraction
While there are some developments in structure solution and refinement, these represent gradual improvements rather than fundamental leaps in methodology. An exception is the assessment of crystal
Characterizing a crystal from an initial native dataset.
  • M. Sawaya
  • Materials Science, Chemistry
    Methods in molecular biology
  • 2007
Methods are presented for characterizing a crystal given an initial X-ray diffraction dataset. These methods can facilitate the structure determination process and illuminate the oligomeric state and
The use of noncrystallographic symmetry averaging to solve structures from data affected by perfect hemihedral twinning
  • C. Sabin, P. Plevka
  • Chemistry, Materials Science
    Acta crystallographica. Section F, Structural biology communications
  • 2016
The noncrystallographic symmetry averaging of the electron-density map corrected errors in the detwinning introduced by the differences between the molecular-replacement model and the crystallized structure.
Methods of space-group determination - a supplement dealing with twinned crystals and metric specialization.
  • H. Flack
  • Physics
    Acta crystallographica. Section C, Structural chemistry
  • 2015
Tables for the determination of space group for single crystals, twinned crystals and crystals with a specialized metric are presented in the form of a spreadsheet for use on a computer. There are 14
Macromolecular crystal twinning, lattice disorders and multiple crystals
Macromolecule crystal structure analyses can be severely hampered by cases of twinning or of lattice disorders or of multiple crystals. However, it is increasingly the case that twinning can readily
Recovery of data from perfectly twinned virus crystals revisited
  • H. Ginn, D. Stuart
  • Chemistry
    Acta crystallographica. Section D, Structural biology
  • 2016
An iterative method of map recovery for perfectly merohedrally twinned crystals in the presence of noncrystallographic symmetry is reimplemented and released and an independent metric of success is
Structural Data on the Periplasmic Aldehyde Oxidoreductase PaoABC from Escherichia coli: SAXS and Preliminary X-ray Crystallography Analysis
X-ray crystallography and SAXS data of PaoABC were collected showing that, in solution, the protein is also an αβγ heterotrimer, and a molecular replacement solution was found for each subunit separately, using several proteins as search models.
Crystallization and preliminary X-ray analysis of a protease inhibitor from the latex of Carica papaya.
A Kunitz-type protease inhibitor purified from the latex of green papaya fruits was crystallized in the presence and absence of divalent metal ions to establish a merohedral twin with two molecules in the asymmetric unit and unit-cell parameters.


[22] Detecting and overcoming crystal twinning.
Solvent content of protein crystals.
Treatment of diffraction data from crystals twinned by merohedry
Crystals of the protein B-phycoerythrin from the red alga Porphyridium cruentum undergo twinning by merohedry in which the two members of the twin are related by rotation about (1,1,-1,0), a symmetry
Twinning by merohedry and X‐ray crystal structure determination
Twins by merohedry can be usefully divided in two classes. Class I: the twin operation is contained in the Laue symmetry of the crystal and twin-related reflexions have equal intensities; in this
Estimation of twinning parameter for twins with exactly superimposed reciprocal lattices
In twinned crystals the intensity contribution from the separate individuals can be estimated from the observed intensities without any knowledge of the actual structure, even when the two reciprocal
A General Theory of X-ray Intensity Statistics for Twins by Merohedry
A general theory of X-ray intensity statistics for twins by merohedry is developed based on mathematical analogy of this problem to a one-dimensional random walk. Probability distribution functions
SHELXL: high-resolution refinement.
The locked rotation function.
  • L. Tong, M. Rossmann
  • Chemistry
    Acta crystallographica. Section A, Foundations of crystallography
  • 1990
The procedure described previously has been generalized and the increased power of this 'locked' rotation function permits a good determination of the orientation of an icosahedral virus in the presence of less than 1% of the possible diffraction data to 7 A resolution.
Structure of deoxyhaemoglobin of the antarctic fish Pagothenia bernacchii with an analysis of the structural basis of the root effect by comparison of the liganded and unliganded haemoglobin structures.
No other residue appears to undergo an R to T change in the immediate neighbourhoods that could account for any significant portion of the Root effect, so at least half of the effect must result either from long-range electrostatic interactions or from a large number of local interactions.
The crystal structure of a novel bacterial adenylyltransferase reveals half of sites reactivity
The homologous active site attachment of ATP and the structural distribution of predicted sequence‐binding motifs in PPAT classify the enzyme as belonging to the nucleotidyltransferase superfamily.