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Spatiotemporal insight into photoactivation of the prototypical B₁₂ photoreceptor CarH is revealed across nine orders of magnitude in time, identifying a transient adduct that distinguishes it from thermally activated B₁₂ enzymes.

The European X-ray free-electron laser (EuXFEL) in Hamburg is the first megahertz (MHz) repetition rate XFEL. Here the authors use lysozyme crystals and microcrystals from jack bean proteins and demonstrate that damage-free high quality data can be collected at a MHz repetition rate.

Although structures of single-domain BLUF proteins—a photoreceptor protein domain that senses blue light—have been determined, there have been no reports of the structure of a BLUF protein containing a functional output domain; for this reason, the mechanism of light activation has remained enigmatic. The first biochemical, structural and mechanistic characterization of a full-length, active photoreceptor containing a BLUF sensor domain and a phosphodiesterase EAL output domain is now reported.

Dietary fibers and SCFAs can exert a protective effect against respiratory syncytial virus (RSV). Here, the authors report that microbiota-derived acetate protects mice against RSV infection via GPR43- mediated type 1 interferon response induction in the lungs.

Ultrafast time-resolved serial femtosecond crystallography is used to investigate a photodissociation reaction in a protein, revealing the strong impact of the pump laser fluence on the structural changes  and the reaction mechanism.

The oxidoreductase (NXR) multiprotein complex is a key enzyme in the nitrogen cycle. A detailed structural and biochemical characterization of NXR from the anammox bacterium Kuenenia stuttgartiensis shows that this complex is a filament-forming protein that catalysers both nitrite oxidation and nitrate reduction, and elucidates the mechanisms governing complex assembly and function.

Bacteriorhodopsin (bR) is a light-driven proton pump. Here the authors combine time-resolved crystallography at a free-electron laser, ultrafast spectroscopy and quantum chemistry to study the structural changes following multiphoton photoexcitation of bR and find that they occur within 300 fs not only in the light-absorbing chromophore but also in the surrounding protein.

Phytochrome photoreceptors are master regulators of plant development. This paper describes 3D structures of soybean phytochrome A in both Pr (inactive) and Pfr (signalling) states, revealing changes that might transmit the light signal to the cell.

Researchers describe a mechanism capable of compressing fast and intense X-ray pulses through the rapid loss of crystalline periodicity. It is hoped that this concept, combined with X-ray free-electron laser technology, will allow scientists to obtain structural information at atomic resolutions.

An environmentally safe means of mosquito control is the application of Bacillus thuringiensis israelensis, which produces a cocktail of four naturally crystalline proteins exclusively toxic to mosquito. Here the authors report the atomic-resolution structures of Bti Cry11Aa and related Btj Cry11Ba solved de novo through Serial Femtosecond Crystallography on naturally-occurring nanocrystals.

Entanglement was observed in top–antitop quark events by the ATLAS experiment produced at the Large Hadron Collider at CERN using a proton–proton collision dataset with a centre-of-mass energy of √s  = 13 TeV and an integrated luminosity of 140 fb⁻¹.

Femtosecond crystallography with an X-ray free-electron laser is used to analyse micrometre-sized protein crystals, generating a high-resolution structure of the protein without previous knowledge of what it looks like.

X-ray fee-electron lasers (XFELs) enable time-resolved crystallography experiments and the structure determination of proteins with little or no radiation damage. However currently it is unknown whether the designated 4.5 MHz maximum pulse rate for the European XFEL could lead to sample damage caused by shock waves from preceding pulses. Here, the authors address this question by performing a X-ray pump X-ray probe experiment on haemoglobin microcrystals at the Stanford XFEL facility that mimics the 4.5 MHz data collection mode and observe structural changes and a drop in diffraction data quality of the crystals.

The local X-ray-induced dynamics that occur in protein crystals during serial femtosecond crystallography (SFX) measurements at XFELs are not well understood. Here the authors performed a time-resolved X-ray pump X-ray probe SFX experiment, and they observe distinct structural changes in the disulfide bridges and peptide backbone of proteins; complementing theoretical approaches allow them to further characterize the details of the X-ray induced ionization and local structural dynamics.

Providing detailed structural descriptions of the ultrafast photochemical events that occur in light-sensitive proteins is key to their understanding. Now, excited-state structures in the reversibly switchable fluorescent protein rsEGFP2 have been solved by time-resolved crystallography using an X-ray laser. These structures enabled the design of a mutant with improved photoswitching quantum yields.

Repetition codes running many cycles of quantum error correction achieve exponential suppression of errors with increasing numbers of qubits.

rsEGFP2 is a reversibly photoswitchable fluorescent protein used in super-resolution light microscopy. Here the authors present the structure of an rsEGFP2 ground-state intermediate after excited state-decay that was obtained by nanosecond time-resolved serial femtosecond crystallography at an X-ray free electron laser, and time-resolved absorption spectroscopy measurements complement their structural analysis.

X-ray free-electron lasers produce bright femtosecond X-ray pulses. Here, the authors use a two-colour X-ray free-electron laser beam for simultaneous two-wavelength data collection and show that protein structures can be determined with multiple wavelength anomalous dispersion phasing, which is important for difficult-to-phase projects.

Ten years after the discovery of the Higgs boson, the ATLAS  experiment at CERN probes its kinematic properties with a significantly larger dataset from 2015–2018 and provides further insights on its interaction with other known particles.

Hydrazine is an intermediate in the process of anaerobic ammonium oxidation which has a major role in the Earth’s nitrogen cycle; the crystal structure of a hydrazine synthase enzyme provides insights into the mechanism of hydrazine synthesis.

The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of structure determination from nanocrystals of macromolecules that cannot be grown in large crystals. Over three million diffraction patterns were collected from a stream of nanocrystals of the membrane protein complex photosystem I, which allowed the assembly of a three-dimensional data set for this protein, and proves the concept of this imaging technique.

A meta-analysis of 17 cohorts of mitochondrial disease patients reveals that OxPhos defects are associated with signs of hypermetabolism. Experiments in patient-derived fibroblast show that mitochondrial OxPhos defects trigger hypermetabolism in a cell-autonomous manner and this is linked to accelerated telomere shortening and epigenetic aging.

It is hoped that quantum computers may be faster than classical ones at solving optimization problems. Here the authors implement a quantum optimization algorithm over 23 qubits but find more limited performance when an optimization problem structure does not match the underlying hardware.

The software Xtrapol8 extracts low occupancy states and can thereby accelerate and facilitate data processing in kinetic, timeresolved and ligand-based crystallographic studies.

Serial femtosecond crystallography is a high-throughput, serial crystallography technique for studying macromolecular crystals at an X-ray free-electron laser. This Primer gives an overview of microcrystallization methods, sample delivery and data analysis for applications including membrane proteins, radiation damage-prone systems and time-resolved experiments.