Volume 15 Issue 10, October 2023

Light is a major driver of the chemistry of the atmosphere and usually involves the photolytic fragmentation of molecules into radicals before their reaction. New results show that formaldehyde, excited by low-energy light, can react with oxygen, opening up alternative atmospheric oxidation pathways.

The intentional interweaving of two different metal–organic framework (MOF) lattices could offer a strategy for combining the disparate properties of the two frameworks within a single MOF material. Now, the rational construction of such hetero-interpenetrated MOFs has been demonstrated.

The factors that control the solubility of a salt are many and varied. Now a set of salts with closely related cations suggests that weak London dispersion-controlled CH···π interactions can dominate solubility, despite the presence of much stronger forces.

Medicinal chemistry efforts typically focus on drug–protein interactions and overlook RNA binding as a source of off-target pharmacology. Now, a new method has been developed to map the interactions of small-molecule drugs with RNA in cells and characterize how these interactions can exert functional effects.

Deuterated compounds are used in many applications such as mass-spectrometry standards, drugs or in organic light-emitting diodes. Now, hydrogen-activated homogeneous pincer complex catalysts can be used to perform selective alkene deuteration with the cheapest available deuterium source, D₂O.

Aryl ethers are useful intermediates in organic synthesis and are found in countless biologically active compounds. Now, through palladium/norbornene cooperative catalysis and incorporation of a polarity-reversed N–O reagent as the O-electrophile, an efficient arene methoxylation approach has been successfully developed.

A multimodal imaging approach is developed to interrogate microorganism–semiconductor biohybrids at the single-cell and single-molecule level for light-driven CO₂ fixation. Application to lithoautotrophic bacterium Ralstonia eutropha biohybrids reveals the roles of two hydrogenases in electron transport and bioplastic formation, the magnitude of semiconductor-to-single-cell electron transport and the associated pathways.

Radiation damage in biological systems by radicals and low-energy electrons formed from water ionization is a consequence of ultrafast processes that follow core-level ionization of hydrated metal ions. More details of the complex pathway are now revealed from the study of aluminium-ion relaxation through sequential electron-transfer-mediated decay.

Understanding of the molecular mechanisms underlying the maturation of protein condensates into amyloid fibrils associated with neurodegenerative diseases has so far remained elusive. Now it has been shown that in condensates formed by the low-complexity domain of the amyotrophic lateral sclerosis-associated protein hnRNPA1, fibril formation is promoted at the interface, which provides a potential therapeutic target for counteracting aberrant protein aggregation.

In the atmosphere, photolysis of formaldehyde generates H and HCO radicals, which then react with O₂ to form HO₂ (important in converting atmospheric carbon to CO₂). Now it has been shown that internally excited formaldehyde can also react with atmospheric O₂ to make HO₂ in a direct, one-step ‘photophysical oxidation’, a mechanism likely to be general in the troposphere.

Interpenetration—in which two or more lattices are catenated—is common in metal–organic frameworks (MOFs). Now a deliberate synthesis of hetero-interpenetrated MOFs, with two distinct lattices, has been developed. It can combine the different properties of the two sublattices in one material, as demonstrated with chirality and catalytic activity, delivering an asymmetric catalyst.

The energy density in redox flow batteries is currently limited by the solubility of dissolved redox species. Now it has been shown that intermolecular C–H···π interactions can disrupt electrostatic forces in these organic electrolytes to improve their solubility in non-aqueous solvents.

Now a reactivity-based RNA profiling strategy can measure the global off-target transcriptome interactions of small-molecule drugs at single-nucleotide resolution. Using this approach, three FDA-approved drugs were evaluated, uncovering pervasive drug–RNA interactions and interactions that perturb RNA functions in cells.

Deuterogenation methods typically introduce only two deuterium atoms per unsaturation. Now the single-step hydrogenative perdeuteration of alkenes has been achieved using H₂ and D₂O, with incorporation of up to 4.9 D atoms per C=C double bond. The reaction is catalysed by a ruthenium pincer complex with a catalytic amount of thiol, which serves as a transient cooperative ligand.

Pd/norbornene cooperative catalysis provides a strategy for arene functionalization, but the electrophile scope is typically limited to ‘soft’ elements such as carbon, nitrogen and sulfur. Now the ortho-C–H methoxylation of aryl halides has been realized using a polarity-reversed N−O reagent and facilitated by a C7-bromo-substituted norbornene mediator.

Understanding interfacial and cellular electron transport is essential for guiding efficiency optimization in microbe–semiconductor biohybrids for energy conversion. A multimodal imaging platform that combines optical imaging and photocurrent mapping can now interrogate such electron-transport pathways at the single-cell level, uncovering different roles of hydrogenases and a microbe’s large electron-uptake capacity.

Radiation damage in biology is largely mediated by radicals and low-energy electrons formed by water ionization and extensive, localized water ionization can be caused by ultrafast processes following the core-level ionization of hydrated metal ions. Now it has been shown that, for Al³⁺ ions, relaxation occurs via sequential solute–solvent electron transfer-mediated decay.

Fluorescent sensors that are responsive only in a specific subcellular location have remained elusive. Now, a chemogenetic sensing platform has been developed to sense glutathione in a user-defined organelle of interest. These tools enable quantitative studies of subcellular glutathione homeostasis using visible or near-infrared wavelengths.

An enzymatic reaction installs endogenous β-amino acids in proteins with unique reactivity. Now it has been shows that this reaction can be used for site-specific modification with tetrazine dienophiles to introduce labels onto target proteins. Applications include generation of a radiolabel chelator-modified Her2-binding Affibody and intracellular, fluorescently labelled cell division protein FtsZ.

The design and construction of a stereo-defined DNA-encoded chemical library, featuring the four different 4-amino-proline stereoisomers as a central scaffold, has now enabled the discovery of potent ligands to proteins of pharmaceutical interest. Parallel screening with closely related isoforms (anti-targets) facilitated the isolation of hits with high selectivity ratios.

Visualizing single-molecule reactions using electron microscopy can be difficult because of potential radiation damage from the electron beam. Now, however, it has been shown that a high-energy electron beam can be used to synthesize metallo-azafullerenes. Atomic-resolution, time-resolved transmission electron microscopy, with the help of computational calculations, is used to monitor the metal-encapsulation dynamics.

Aluminium and silicon, two Earth-abundant, well-understood elements, typically form weak Al–Si bonds. Now, complexes featuring an anionic Al–Si core stabilized by bulky substituents and a Si–Na interaction have been isolated. This Al–Si interaction possesses partial double bond character, which can be increased by sequestration of the sodium counterion.

Inspired by the design of peptide and nucleic acid sequences to adopt particular three-dimensional shapes, natural glycan motifs have now been combined to construct a glycan that adopts a hairpin conformation in water. Thus a designed glycan can now autonomously fold into a stable secondary structure absent in nature.

The streamlined synthesis of multiple (proto)biomolecules from common starting materials is a key goal of prebiotic chemistry. Now, a one-pot synthesis of ribo-aminooxazoline (a precursor for prebiotic nucleotide synthesis) from HCN has been achieved. Additionally, the two moieties used in extant terpenoid biosynthesis have been accessed, with all carbon atoms also originating from HCN.

Few explosives are better-known to non-chemists than trinitrotoluene (TNT). Thomas M. Klapötke reflects on the enduring appeal of TNT and whether its starring role as an explosive is nearing its end.