Current trends in macromolecular model refinement and validation

The Guest Editors provide an introduction to the special issue of articles based on talks at the CCP4 Study Weekend 2022, which is available at https://journals.iucr.org/special_issues/2023/CCP42022/.

Modes and model building in SHELXE

All alternative SHELXE modes, using single or combined sources of starting phase information, are described. Side-chain tracing now completes model building in SHELXE to enhance density modification.

The TR-icOS setup at the ESRF: time-resolved microsecond UV–Vis absorption spectroscopy on protein crystals

A setup to measure time-resolved UV–Vis absorption spectra from small protein crystals using a pump–probe scheme with microsecond-to-second delays is described.

Deep residual networks for crystallography trained on synthetic data

Artificial intelligence was used to characterize the diffraction in images from serial and rotation crystallography experiments. Forward simulations were used to train models to infer B factors, resolutions and the presence of crystal splitting from single diffraction images.

Preparation and characterization of inactivated tick-borne encephalitis virus samples for single-particle imaging at the European XFEL

A purification and concentration scheme for the tick-borne encephalitis virus (TBEV) vaccine was developed along with a quality-control protocol that enabled substantial amounts of highly concentrated non-aggregated suspension to be produced. This approach allowed single-particle imaging experiments to be conducted for this sample at the European XFEL, which resulted in distinct patterns of diffraction. In order to illustrate the advantages of the proposed protocols, the cryo-EM structure of TBEV has been determined.