Further adventures of the perovskite family

The perovskites are an intensely studied class of materials, with a breadth of possible compositions made even wider by the possibility of incorporating molecular ions. Here the context is discussed of a newly reported metal-free perovskite with the H₃O⁺ ion on the B site.

To bind, or not to bind, that is the question…

The unexpected findings that are described by Czub et al. [IUCrJ (2022), 9, 551–561] provide a very interesting study demonstrating how small differences in structure can result in significant changes in the relative affinities of the seemingly promiscuous binding sites that are seen with serum albumins.

Serial small- and wide-angle X-ray scattering with laboratory sources

Commercial X-ray scattering instruments were assessed for their ability to perform rapid flow-based structural analysis using micro- and millifluidic sample environments. These studies demonstrate that serial collection of small- and wide-angle X-ray scattering data from small-molecule crystals and nanoparticles is now possible with laboratory instruments.

Metal-free enantiomorphic perovskite [dabcoH₂]²⁺[H₃O]⁺Br⁻₃ and its one-dimensional polar polymorph

A metal-free and ammonium-free perovskite ABBr⁻₃ (where A = 1,4-di­aza­bicyclo­[2.2.2]octane dication and B = H₃O⁺) has been obtained in two forms: polymorph α with corner-sharing, and polymorph β with face-sharing octahedra [H₃O⁺]Br₆.

Organism-specific differences in the binding of ketoprofen to serum albumin

Ketoprofen exhibits different binding-site preferences when interacting with mammalian albumins from different species. The drug-binding properties of albumins cannot easily be predicted based only on a complex of albumin from another species even when the drug-binding sites exhibit a high degree of conservation between species.

Neutron crystallographic analysis of the nucleotide-binding domain of Hsp72 in complex with ADP

The neutron crystallographic structure of an Hsp72–ADP complex is reported.

Accurate crystal structure of ice VI from X-ray diffraction with Hirshfeld atom refinement

Accurate crystal structures of H₂O, D₂O and mixed (50%H₂O/50%D₂O) ice VI obtained by Hirshfeld atom refinement (HAR) of high-pressure single-crystal synchrotron and laboratory X-ray diffraction data are presented. It was possible to obtain O—H bond lengths and anisotropic displacement parameters for disordered hydrogen atoms which are in good agreement with the corresponding results of single-crystal neutron diffraction data. These results show that HAR combined with X-ray diffraction can compete with neutron diffraction in detailed studies of polymorphic forms of ice and crystals of other hydrogen-rich compounds.

Self-transformation of solid CaCO₃ microspheres into core-shell and hollow hierarchical structures revealed by coherent X-ray diffraction imaging

Coherent X-ray diffraction imaging and 3D X-ray fluorescence were used to visualize in 3D the self-transformation of polycrystalline microspheres of calcium carbonate into hollow and core-shell microspheroid hierarchical structures.

Real-space texture and pole-figure analysis using the 3D pair distribution function on a platinum thin film

An approach is described to study texture in nanostructured materials by utilizing the 3D pair distribution function. It is demonstrated how to measure, process and analyze data to obtain the textured 3D pair distribution function on a fiber-textured platinum thin film.

Refinement of anomalous dispersion correction parameters in single-crystal structure determinations

Refined anomalous dispersion values provide an easy and reliable way to correct for inelastic scattering effects of the electronic environment unique to each structure. Herein, we introduce the implementation of this refinement in OLEX2 and discuss its usage and perspectives.

Complementarity of neutron, XFEL and synchrotron crystallography for defining the structures of metalloenzymes at room temperature

The determination of the structure of the multifunctional globin dehaloperoxidase using multiple room-temperature methods is described. Structures obtained by serial femtosecond crystallography, serial synchrotron crystallography, neutron diffraction and serial Laue crystallography are compared and two oxidation states of the enzyme are contrasted.

The Haemophilus influenzae HipBA toxin–antitoxin system adopts an unusual three-com­ponent regulatory mechanism

The crystal structure of HipA^N, an unusual N-terminal com­ponent of the HipA toxin from Haemophilus influenzae, was determined at 2.70 Å resolution. A combined study on this unique three-com­ponent HipBA toxin–antitoxin system provides further insights into the regulatory mechanism of the HipBA toxin–antitoxin system.

Higher resolution in cryo-EM by the combination of macromolecular prior knowledge and image-processing tools

This article explores the use of the deep learning approach deepEMhancer as a regularizer in the RELION refinement process. deepEMhancer introduces prior information derived from macromolecular structures and contributes to noise reduction and signal enhancement, as well as a higher degree of isotropy, with a direct effect on image alignment and a reduction of overfitting during iterative refinement.

Water: new aspect of hydrogen bonding in the solid state

The geometric criteria for defining attractive water–water interactions should be broader than the classical hydrogen-bonding criteria given that attractive antiparallel interactions also exist.

A general method for directly phasing diffraction data from high-solvent-content protein crystals

This paper describes a practical method for ab initio phasing of diffraction data collected from high-solvent-content protein crystals (solvent content >70%). Unlike traditional direct methods, this procedure leverages the powerful constraint of solvent flatness, and works at the modest resolutions (2.0–3.5 Å) and with the large numbers of atoms, that are typical of protein crystallography.

Changes in active-site geometry on X-ray photoreduction of a lytic polysaccharide monooxygenase active-site copper and saccharide binding

The recently discovered lytic polysaccharide monooxygenases (LPMOs) are Cu-containing enzymes capable of degrading polysaccharide substrates oxidatively. Here we have monitored the Cu-site geometry in two AA9 LPMOs, one from Lentinus similis (LsAA9_A) and one from Thermoascus auranti­acus (TaAA9_A), as the active-site Cu is photoreduced in the X-ray beam. In addition, we have characterized in detail the structural effects of oligosaccharide binding in differently photoreduced states of LsAA9_A.

The tem­per­ature-dependent conformational ensemble of SARS-CoV-2 main protease (M^pro)

X-ray crystallography at variable tem­per­ature for SARS-CoV-2 M^pro reveals a com­plex conformational landscape, including a mobile metal at the catalytic dyad, mercurial conformational heterogeneity at various sites, and an intra­molecular network bridging the active site and dimer inter­face.

Qu­antitative analysis of diffuse electron scattering in the lithium-ion battery cathode material Li_1.2Ni_0.13Mn_0.54Co_0.13O₂

The stacking fault probability in submicrometre-sized crystals of Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ was refined through the quantitative analysis of diffuse electron scattering.

Refining perovskite structures to pair distribution function data using collective Glazer modes as a basis

A model has been developed for refining rigid octahedral rotations in perovskites and demonstrated to model pair distribution function data of CaTiO₃.