The International Union of Crystallography (IUCr) and its journals are celebrating their 75th anniversary. In this editorial, some of the publication achievements are highlighted and prospects for the future reviewed in an emerging open-access world.

This article reviews phase evaluation in macromolecular crystallography. It accompanies the 2023 Ewald Prize lecture at the 26th IUCr Congress, paying tribute to Paul Ewald's far-reaching influence.

Interoperability of scientific data within crystallography has been achieved to a high level by the adoption of standard exchange formats and protocols. Extending such interoperability across other disciplines is a goal of the International Science Council Committee CODATA, to which the IUCr has been a leading contributor. Our article combines a description of the importance of interoperability for addressing grand challenges with a desire to stimulate the crystallographic community to continue exploring this topic.

Structural sciences serve as a bridge between the fundamental understanding of materials and their applications, by elucidating the atomic and molecular intricacies that define the performance of functional materials. Spanning diverse fields, from energy storage to catalysis, this article emphasizes the evolving experimental techniques that have revolutionized our knowledge of structures and dynamic processes, positioning structural science as the essential guide to the future development of functional materials.

Since they do not belong to the class of subperiodic groups, line groups thus far have been beyond the scope of symmetries traditionally studied in crystallography, although they describe the symmetry of numerous `one-dimensional' crystals (i.e. monoperiodic structures). Therefore, together with an overview of frieze, rod and layer groups, a brief introduction to line groups is presented.

This paper proposes a rigorous definition of a periodic structure as an equivalence class of periodic sets under rigid motion, which is a composition of translations and rotations.

The 26th IUCr congress held in Melbourne brought discussions on micro-crystallization and in vivo crystallography within structural biology to the forefront, highlighting innovative approaches and collaborative efforts to advance macromolecular research.

Using synchrotron radiation, diffraction data extending to 0.70 Å resolution were collected from crystals of the small protein crambin at room temperature (297 K), and the structure was refined with spherical-atom approximation to an R factor of 0.0591, revealing (i) protein regions with multiple conformations, (ii) extended water networks correlated with protein conformations and (iii) minimal radiation damage. The structure sets a standard for room-temperature refinement of macromolecular targets and provides accurate data for modeling protein–solvent interactions.

The RCSB PDB research-focused web portal at https://www.rcsb.org/ provides important tools and resources to search, visualize and analyze experimentally determined 3D biostructures alongside computed structure models of proteins predicted using artificial intelligence/machine-learning based tools.

This topic review summarizes structures of chaperones complexed with MHC-I, the structural principles that govern peptide exchange and the mechanism in antigen presentation.

Formate de­hydrogenases (FDHs) catalyze the two-electron oxidation of formate to carbon dioxide. This article presents recent progress in the structural analysis of FDHs together with their potential biotechnological applications.

Photosystem II is the enzyme responsible for generating nearly all the oxygen in the atmosphere. Room-temperature time-resolved crystallography and spectroscopy measurements at X-ray free-electron lasers help to elucidate the sequence of events in the water oxidation reaction of photosystem II leading to the formation of di­oxy­gen from two molecules of water.

Diffuse X-ray scattering is used to characterize the time dependence of the liquid phase emerging from femtosecond laser-induced melting of polycrystalline gold thin films using an XFEL. Its structure factor and partial pair distribution function confirm the liquid origin of the diffuse scattering. The liquid fraction increases with a characteristic rise-time of 13 ps.

Platinum(II) complexes exhibit intense luminescence based on their molecular arrangement and chromic luminescence, which is a color change in response to gentle stimuli such as vapor exposure or weak mechanical forces. Both the molecular and the crystal designs for soft crystals are critical to effectively control the chromic phenomenon of platinum(II) complexes.

In structural biology, the analogy of a key (ligand) fitting a lock (protein) is commonly used to describe the binding process. In this context, we illustrate the evolutionary development of diverse locks that exhibit specific binding to a shared key: Neu5Ac. The intricate specificity of the interaction between various locks and the common key (Neu5Ac) is explored in our review.

This review examines the use of ultra-small angle X-ray scattering (USAXS), a nondestructive technique for analyzing the multi-scale microstructures of hard materials such as ceramics, metals and composites. It discusses the principles, benefits and challenges of USAXS, along with its potential to advance materials development and optimize manufacturing processes, while also considering future enhancements through multimodal characterization and machine learning.

The TIR (Toll/interleukin-1 receptor) domains are found in proteins with roles in the immune systems of humans, plants and bacteria. A combination of structural methods ranging from X-ray and electron crystallography to cryogenic electron microscopy and nuclear magnetic resonance spectroscopy has been required to understand how these domains contribute to signalling, highlighting the complementarity of different structural approaches.

Biological materials obtain their properties through hierarchical structuring. Understanding such materials calls for multimodal and multiscale approaches. Based on two example systems, bone and shell, we discuss current analytical approaches, their capabilities and limits, and how to tie them together to fully cover the different length scales involved in understanding materials' functions. We will further discuss advances in this area and future developments, the possible roadblocks (radiation damage, data quantity, sample preparation) and potential ways to overcome them.

This topical review discusses the recent progress in low-dose high-resolution imaging of metal–organic framework materials and gives a brief outlook on possible future directions.

In this work, a reversible non-invasive light-induced mesophase transition from lamellar to cubic Pn3m is observed in mixed azo­benzene-lipid and phospho­lipid vesicles using small-angle X-ray scattering.

A binding approach based on electronic force density fields was used to describe the structures of the molecule, dimer and crystal of a uracil derivative. Transferable multipole pseudo-atoms were successfully used to reconstruct the inner-crystal electronic force density fields.

AlphaFold predictions can be used both as a starting point for structure determination and as a method of model optimization. The Phenix PredictAndBuild tool automates iterative prediction and model building, yielding a density map and model starting with sequence information and crystallographic data.

This contribution outlines how to obtain perfect precise colorings of tilings, and illustrates this by obtaining perfect precise colorings of some families of k-valent semiregular planar tilings with k colors.

Advances in X-ray hardware and software have revolutionized crystallography: now crystal structures can be routinely solved first, with publication-quality datasets collected second. This same approach now allows multi-grain crystallography to be completed in the laboratory with Cu Kα X-rays.

All the possibilities for permissible (mismatch-free) walls between monoclinic domains of pseudocubic ferroic perovskites are analyzed. Analytical expressions are derived for the orientation of such walls, the orientation relationship between the lattice vectors and the separation between Bragg peaks diffracted from matched domains.

Following the previous work [Biran & Gorfman (2024). Acta Cryst. A80, 112–128], all the possibilities for permissible (mismatch-free) walls between monoclinic domains of pseudocubic ferroelectric perovskites of M_C type are analyzed. The study yields analytical expressions for the orientation of such walls, the orientation relationship between the lattice vectors and for the separation between Bragg peaks diffracted from matched domains.

X-ray absorption spectroscopy (XAS) measurements of N-truncated amyloid-β samples were corrected for systematic effects such as dead time, detector efficiencies, monochromator glitches, self-absorption, radiation damage and noise at higher wavenumbers k, permitting hypothesis testing in structural refinements. A new protocol was developed using extended X-ray absorption fine structure data analysis for monitoring radiation damage in real time and post-analysis.

A dipropyl-substituted isoindigo derivative has three polymorphs with different mol­ecular conformations and arrangements.

A single-particle structure determination pipeline is implemented in the open-source software xFrame, which includes methods for determining rotational invariants from X-ray scattering patterns and performing structure reconstructions by iterative phasing of rotational invariants.

A simple symmetric 2D scan using a point focus beam was used to determine the fibre axis of fibre-textured satin spar samples. A geometric explanation of the `wing' feature formed by the diffraction spots in 2D scans helps to visualize the nature of the reciprocal layers of the fibre-textured samples through wide-range reciprocal space mapping.

The 3N-dimensional maxima of the square of the wavefunction, the so-called Born maxima, show beyond doubt that the electronic structure of atoms persists in molecules, either in their original ground state or some low-lying excited state. The electron density is only a low-dimensional projection of this much richer landscape.

The disequilibrium Sn content in Pb inclusions present in ancient (Sn,Cu)-bronze samples may in principle be used for authentication purposes. The present article explores the applicability of a method based on precise diffraction measurement of the Pb lattice parameter.

A new polymorph of 1,3-diacetylpyrene that is luminescent in the solid state and a prominent negative thermal expansion material has been obtained from its melt. A thorough structural characterization of this new crystal form was performed in a wide temperature and pressure range using single-crystal X-ray diffraction. Structural studies have been combined with steady-state UV–Vis spectroscopy and periodic density functional theory calculations. A previously published methodology of crystal placement in a diamond anvil cell has been successfully applied in predicting optimal 2°AP-β sample orientation, ensuring >80% data coverage and enabling unrestrained Hirshfeld atom refinements for high-pressure structures as well as analysis of anharmonic oscillations.