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Photoredox catalysis promises transformative advances in proximity labeling and noninvasive therapy, yet photocatalysts rarely combine low-energy light absorption with high excited-state potentials. Here, the authors report Ru-based bio-photocatalysts that integrate greenlight absorption with strong redox power, enabling selective protein and phenol coupling.

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.

Fusion proteins containing blue-light-activated domains have been used as molecular switches to investigate cell signalling, but molecular understanding of the transduction pathway is lacking. Here, MD simulations are used to elucidate the transduction mechanism in a light oxygen voltage2-Ja photosensor.

Light-controlled gating of ion transport across membranes occurs in nature via channelrhodopsin nanochannels. Here, the authors show facile non-covalent approach towards light-responsive biomimetic nanochannels using host–guest interactions between a negative pillararene host and a positive azobenzene guest.

An artificial reaction centre has been designed that contains a benzimidazole–phenol model of the Tyr–His relay in photosystem II. It has been seen to mimic both the short internal hydrogen bond of the natural relay, and — using electron paramagnetic resonance —the relaxation behaviour that accompanies proton-coupled electron transfer in photosystem II.

Azobenzene-based photoswitchable drugs traditionally require activation with UV-blue light having poor tissue penetration. Here, the authors show triplet sensitized photoisomerization of an azo drug with far-red and NIR light, allowing deep tissue penetration and in vivo heart rate control in frog tadpoles.

The color of rhodopsins is regulated by the interaction of the chromophore with its counterion. Here the authors introduce a computational model showing that color tuning can be described in terms of virtual counterion migration and delocalization pathways.

A brief description of the basic steps required to control cellular function with optogenetics is presented.

Time-resolved serial crystallography at XFELs reveals ultrafast photochemical reactions, but high laser densities can cause photodamage to biological samples. Here, the authors study the early K-intermediate in bacteriorhodopsin at high power, showing overall conformation remains robust over a wide range.

The photocurrent generated by a single photosynthetic protein can be measured using a scanning near-field optical probe that functions as both an electrode and a light source.

Protein modules that dimerize rapidly upon exposure to light are reported. They permit light-induced control of dimerization of fused protein targets and can be manipulated with two-photon illumination for experiments in thick samples and in vivo.

De novo development of a simplified photosynthetic reaction center protein can clarify practical engineering principles needed to build enzymes for efficient energy conversion. Here, the authors develop an artificial photosynthetic reaction center that functions without the need for sacrificial electron donors or acceptors.

Iridium-based photosensitizers exhibit good photocatalytic performance, but the in vivo applications are hindered by conventional O₂-dependent Type-II photochemistry and poor absorption. Here, the authors report a general metallopolymerization strategy for engineering iridium complexes exhibiting Type-I photochemistry and enhancing absorption intensity in the blue to near-infrared region.

Here the authors combine 19 F NMR and femtosecond transient absorption to characterise the structural origin of the multiphasic quenching dynamics in various species of BLUF domains, highlighting the importance of the heterogeneous active-site H-bond network.

It is unclear why flying insects congregate around artificial light sources. Here, the authors use high-speed videography and motion-capture, finding that insects fly perpendicular to light sources due to a disruption of the dorsal light response.

Photoinduced electron transfer forms the basis for photosynthesis and DNA repair. Ultrafast structural changes recorded for a DNA-repairing photolyase now reveal specific and directed protein motions accompanying the electron transfer.

Azo compounds are widely used in the photo-induced regulation in biological systems. Here, the authors develop a nanosystem comprising an azo-fluorescent switch, in which the visible light-responsiveness enables the control of the system and monitorization using fluorescence imaging.

Disulfide bonds play a key role in the stability of proteins. Here, the authors show such bonds are efficiently reformed after UV photolysis in L-cysteine in solution using femtosecond X-ray absorption spectroscopy and theoretical calculations.

Photoswitchable ligands can reversibly modulate receptor activity upon light-induced isomerization, yet the impact of structural changes on efficacy is not well understood. Here, the authors use molecular dynamics simulations to investigate two azobenzene-based 5–HT2A receptor ligands with different methoxy substituent positions, revealing that ligand insertion depth into the binding pocket is a crucial determinant of efficacy.

The metallophilic interaction between cyclometalated palladium complexes can facilitate supramolecular nanostructure formation in living mice, providing a phototoxic prodrug with a long circulation time and high tumour-targeting efficiency. Upon green light irradiation, this palladium-based drug destroys solid tumours, leaving non-irradiated organs intact.

Acylhydrazones are often found in compounds across screening databases, and numerous bioactive acylhydrazones exist. This functional group can isomerize between E and Z in response to light or upon exposure to thiols. Now, E/Z isomerization is found to impact activities of bioactive acylhydrazones and should be routinely analysed.

Two-photon absorption (TPA) affords unparalleled spatiotemporal resolution for bioimaging, but the photo-oxidation tends to weaken the photoluminescence in vivo, limiting the usefulness of TPA probes. Here, the authors report self-assembling near-infrared cyanine dye-based nanoprobes of enhanced TPA fluorescence imaging capacity based on a photo-oxidation enhanced emission mechanism.

This study explores how the photosynthetic alga Nannochloropsis oceanica, rapidly adapts to changing light conditions, using a short-term “memory" system involving the xanthophyll cycle, which is widespread in photosynthetic organisms.

Structural analysis of a protein complex in the circadian clock of Drosophila reveals how a light-sensing cryptochrome recognizes and engages its target.

Photoluminescent gold clusters have unique chemical and physical properties based on their perturbed electronic structures. Here, the authors report the synthesis of carbon-centered Au(I)-Ag(I) clusters with high phosphorescence quantum yields using N-heterocyclic carbene ligands.

Phytochromes are photoreceptors responsible for sensing light in plants, fungi and bacteria. Here the authors use computational simulations to reveal the molecular mechanism of photoactivation and characterize the involved reaction intermediates.

Orange Carotenoid protein (OCP) is the only photoreceptor with a carotenoid for sensing. Here, the authors report crystal structures of the early OCP photoproduct, suggesting that photo-sensing involves single bond isomerization.

Despite enormous potential of solar-driven biocatalysis, most living systems lack photoactive proteins and require toxic and expensive synthetic materials limiting the performance. Here, a class of natural photoconductors is demonstrated through sub-picosecond heme-to-heme electron transfer in bacteria-produced protein nanowires.

Bio-hybrid photoelectrochemical systems integrate microbial components with abiotic conductors/semiconductors for solar fuels and chemical conversion. Here, the authors analyze the bottlenecks related to catalytic efficiency, stability and scalability, and propose strategies to address these challenges.

Light-oxygen-voltage (LOV) photoreceptors perceive blue light to elicit spatio-temporally defined cellular responses, and their signalling process has been extensively characterized. Here the authors report that the light signal is still transduced in the absence of a conserved Gln residue, thought to be key.

Developing stimuli-responsive bioorthogonal tetrazine ligations remains highly challenging, but a versatile approach that uses photocaged dihydrotetrazines has now been developed. Photouncaging results in the spontaneous formation of reactive tetrazines that rapidly react with dienophiles such as trans-cyclooctenes. As a demonstration, the method was used for live-cell labelling with single-cell precision and light-triggered drug delivery.

The cytochrome P450 enzyme CYP1B1 is overexpressed in a variety of tumors, and is correlated with poor treatment outcomes; thus, it is desirable to develop CYP1B1 inhibitors to restore chemotherapy efficacy. Here the authors describe the creation of light-triggered CYP1B1 inhibitors as “prodrugs”, and achieve >6000-fold improvement in potency upon activation with low-energy (660 nm) light.

Femtosecond time-resolved X-ray solution scattering (fs-TRXSS) measurements provide information on the structural dynamics of proteins in solution. Here, the authors present a structure refinement method for the analysis of fs-TRXSS data and use it to characterise the ultrafast structural changes of homodimeric haemoglobin.

Metabolites can distinguish pathogenic from healthy cells, but they are hard to couple to current photosensitizers without altering their biological activity. Here the authors design a new family of photosensitizers that retain metabolite function to target pathogenic cells and ablate them by photodynamic therapy.

Voltage imaging is a powerful technique for studying electrical signalling in neurons. A palette of bright and sensitive voltage indicators has now been developed via enzyme-mediated ligation and Diels–Alder cycloaddition. Among these, a far-red indicator faithfully reports neuronal action potential dynamics with an excitation spectrum orthogonal to optogenetic actuators and green/red-emitting biosensors.

UVR8 is a plant photoreceptor that dissociates into monomers after sensing UV. Here, via ultrafast spectroscopy and computational calculations, the authors describe the dynamics of charge separation and charge neutralization in UVR8 and describe how these unzip interactions at the dimer interface.

Recent experimental evidence shows a new type of intrinsic fluorescence in biomolecules void of aromatic chemical compounds whose origin is unclear. Here, the authors use non-adiabatic AIMD simulations to show a potential carbonyl-lock mechanism originating this phenomenon.

Malakar et al. investigate the photochemical dynamics in the isomerization of bacteriorhodopsin light and dark-adapted forms and in the first photocycle intermediate, K. The results prompt a reevaluation of the counter ion model, revealing that a different protonation then that shown in the classic quadrupole so far considered must be employed to account for the experimental data.

The photochemistry of the pyruvate anion plays an important role in the Earth’s atmosphere and aqueous environments. Here, the authors show that excitation of aqueous pyruvate by 200 nm light leads to decarboxylation with a quantum efficiency of 20%, while excitation by 340 nm light does not cause a reaction.

The number of usable light-responsive enzymes is limited, despite the potential biotechnological applications. Here, the authors report a flavoprotein monooxygenase which is controllable by blue light illumination, and propose a mechanism involving protein-mediated radical photoreduction of FAD via a semiquinone intermediate.

Pump-probe experiments in the gas phase usually target neutral molecules. Here the authors couple an electron spray source with ultrafast pump-probe UV-Vis spectroscopy, to follow the ππ*-πσ* coupling in tryptophan-based ions.

Pump–probe measurements conventionally achieve femtosecond time resolution for X-ray crystallography of reactive processes, but the measured structural dynamics are complex. Using coherent control techniques, we show that the ultrafast crystallographic differences of a fluorescent protein are dominated by ground-state vibrational processes that are unconnected to the photoisomerization reaction of the chromophore.

The generation of reactive oxygen species (ROS) in photodynamic cancer treatments is limited by low intraturmoural oxygen availability. Here the authors show that irradiation of a silicon phthalocyanine leads to uncaging of a biologically active molecule or to ROS formation in an oxygen-dependent manner.

Isotope effects provide deep insight into mechanisms of chemical and biochemical processes. Now, it has been shown that the pattern of isotopic substitution of the isomerizing bond of the retinal chromophore in the visual pigment rhodopsin significantly alters the reaction quantum yield—revealing a vibrational phase-dependent isotope effect.

By using in vivo ultrafast TA spectroscopy, extraction of electrons directly from photoexcited PSI and PSII in cyanobacterial cells using exogenous electron mediators is demonstrated.

A genetically encoded phototrigger based on a xanthone amino acid can expand the scope of time-resolved serial femtosecond crystallography beyond naturally photoactive proteins. This approach has been used to uncover metastable reaction intermediates that occur prior to C–H bond activation in a human liver fatty-acid-binding protein mutant.