issue contents

ISSN: 2053-2733

May 2021 issue

Highlighted illustration

Cover illustration: One of the major bottlenecks in macromolecular X-ray powder diffraction has always been the loss of structural information due to the severe overlap of powder diffraction peaks. In this issue, Spiliopoulou et al. [Acta Cryst. (2021), A77, 186–195] report an improved data-collection strategy using a MYTHEN II strip detector that leads to substantial improvement of angular resolution at low 2θ. The cover image shows selected amino acids of the refined structure of octreotide.


lead articles

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The distinctive features of the probes used in understanding the structure of matter focusing on biological sciences, but not exclusively, are described in the modern context to minimize the consequences of artefactual information in data interpretation. The precision and accuracy of both data and technique are revisited. A variety of structural results are described that reach beyond reductionism to the whole biological organism. All these aspects open new doors to change and extend the foundations of the structural sciences.

research papers

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The complete structure of a pharmaceutical molecule, octreotide (PDB code 6vc1), obtained by X-ray powder diffraction data at 1.87 Å resolution, using a MYTHEN II detector system at the Swiss Light Source, is reported.

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The `digital' large-angle convergent-beam electron diffraction (D-LACBED) method uses computer control of a transmission electron microscope to collect hundreds of diffraction patterns from a region a few nanometres in size, which are combined into a single data set. The sensitivity of the resulting patterns to crystal structure is explored using the Ruddlesden–Popper oxide Ca3Mn2O7 and it is found that refinement of atomic coordinates can be performed to sub-picometre precision.


research papers

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Binary and multinary nitrides in a wurtzitic arrangement are very interesting semiconductor materials. The group–subgroup relationship between the different structural types is established.

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The dynamical effect in high-energy electron diffraction in non-symmorphic space-group crystals is discussed using Bloch waves. A contrast mechanism for Gjønnes–Moodie lines by Bloch waves is described.

addenda and errata

book reviews

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