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Related Concept Videos

Determination of Crystal Structures01:29

Determination of Crystal Structures

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In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...
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Imperfections in Crystal Structure: Point, Line and Plane Defects01:25

Imperfections in Crystal Structure: Point, Line and Plane Defects

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A perfect crystal, in theory, has a uniform structure with the same unit cell and lattice points throughout. However, any deviation from this periodic arrangement is known as an imperfection or defect. These defects can be categorized into three types: point, line, and plane defects.Point defects occur when there is a deviation from the ideal due to missing atoms, displaced atoms, or additional atoms. These imperfections might occur due to imperfect packing during crystallization or because of...
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Imperfections in Crystal Structure: Stoichiometric Point Defects01:26

Imperfections in Crystal Structure: Stoichiometric Point Defects

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Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
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Imperfections in Crystal Structure: Non-Stoichiometric Defects01:29

Imperfections in Crystal Structure: Non-Stoichiometric Defects

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Non-stoichiometric defects refer to a type of defect in the crystal structure of a compound where the ratio of its constituent elements deviates from the ideal stoichiometric ratio. There are two main types of non-stoichiometric defects: metal excess defects and metal deficiency defects.Metal excess defects occur when there is a slight surplus of metal ions than what is required by the stoichiometric ratio of the compound. For example, heating a sodium chloride crystal in sodium vapor results...
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X-ray Diffraction of Biological Samples01:10

X-ray Diffraction of Biological Samples

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X-ray diffraction or XRD is an analytical tool that utilizes X-rays to study ordered structures such as crystalline organic and inorganic samples, polycrystalline materials, proteins, carbohydrates, and drugs.
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are  scattered by the electron clouds around the sample atoms. The  X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal...
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X-ray Crystallography02:18

X-ray Crystallography

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The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
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Related Experiment Video

Updated: Mar 8, 2026

Crystallization and Structural Determination of an Enzyme:Substrate Complex by Serial Crystallography in a Versatile Microfluidic Chip
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Crystal pathologies in macromolecular crystallography.

Zbigniew Dauter1, Mariusz Jaskólski2

  • 1Macromolecular Crystallography Laboratory, National Cancer Institute, Argonne National Laboratory, Argonne, IL 60439, USA.

Postepy Biochemii
|January 30, 2017
PubMed
Summary
This summary is machine-generated.

Macromolecular crystals, often containing ~50% water, can exhibit pathologies like pseudosymmetry and twinning that complicate structural analysis. Understanding these defects is crucial for accurate macromolecular structure determination.

Keywords:
aperiodic crystalscommensurate modulationcrystal twinningdiffraction anisotropydiffuse scatteringincommensurate modulationlattice-translocation defectsmerohedrymodulated structuremosaicitynon-crystallographic symmetry (NCS)order-disorder (OD)pseudosymmetryquasicrystalssuperstructuretranslational NCS

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Microcrystallography of Protein Crystals and In Cellulo Diffraction
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Last Updated: Mar 8, 2026

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Area of Science:

  • Crystallography
  • Structural Biology
  • Materials Science

Background:

  • Macromolecular crystals, including proteins and nucleic acids, typically contain a high water content (~50%).
  • Beyond common defects, these crystals can present pathologies that hinder structural interpretation.
  • These pathologies include pseudosymmetry, lattice-translocation defects (order-disorder twinning), and crystal twinning.

Purpose of the Study:

  • To elucidate the various structural pathologies affecting macromolecular crystals.
  • To highlight the challenges these defects pose for X-ray diffraction data processing and structure solution.
  • To provide a comprehensive overview of crystal defects beyond simple physical imperfections.

Main Methods:

  • Review of crystallographic defect types in macromolecular systems.
  • Analysis of diffraction data implications for various crystal pathologies.
  • Categorization of order-disorder phenomena in crystal lattices.

Main Results:

  • Identified pseudosymmetry (non-crystallographic symmetry) and lattice-translocation defects (OD-twinning) as significant challenges.
  • Described crystal twinning and modulated structures where periodic order is compromised.
  • Noted other phenomena like high mosaicity and anisotropic diffraction that impede structure determination.

Conclusions:

  • Structural pathologies in macromolecular crystals, including pseudosymmetry and twinning, significantly complicate structure solution.
  • Understanding these defects is essential for accurate interpretation of diffraction data.
  • Further research into defect mitigation and advanced analysis techniques is warranted for challenging crystal systems.