Volume 12 Issue 9, September 2020

Stay-at-home policies invoked in response to COVID-19 have led to well-publicized drops in some air pollutants. The extent to which such reductions translate to improved air quality is dictated by not only emissions and meteorology, but also chemical transformations in the atmosphere.

There are plenty of online resources to ensure that learning can continue for students who cannot access universities during a pandemic, but what options are there for practical aspects of science courses? Daren J. Caruana, Christoph G. Salzmann and Andrea Sella offer a manifesto for home-based experiments.

Controlling the formation of ordered and predictable patterns in dissipative reaction–diffusion processes is challenging. Now, liquid vibrations induced by audible sound have been shown to direct the formation of spatiotemporal patterns in switchable chemical systems and assemblies.

White phosphorus is a prominent source of P atoms but has remained difficult to activate without using transition metals. Now, a bidentate ligand based on silicon(ii) donors has successfully stabilized a P₂ moiety, and the resulting complex acts as a transfer reagent for P^– anions.

An approach to design artificial intrinsically disordered proteins using a short peptide as a repeating unit has been reported. This design enables the phase behaviour of the protein to be finely tuned inside cells and enabled the formation of phase-separated condensates that can modulate chemical reactions.

Recent research has shown that vibronic coherences are one of the primary drivers for ultrafast light-induced processes. Now, ultrafast spectroscopy has been used to uncover vibronic coherences in the excited-state dynamics of an iron complex, leading to its redesign and the drastic prolonging of its excited-state lifetime.

Enzymes that methylate using S-adenosyl-l-methionine — nature’s methyliodide — are abundant and often promiscuous; however, a preference for alkylation over methylation has been neither observed in nature nor engineered. Now, carboxymethylation has been demonstrated using engineered methyltransferases.

Chemical systems can show complex behaviour that is not seen in individual molecules or reactions. Helena S. Azevedo, Sarah L. Perry, Peter A. Korevaar, and Dibyendu Das report on the emergence of this complex behaviour, which was discussed at the Virtual Symposium on Systems Chemistry

Photoinduced isomerization reactions, including ring-opening reactions, lie at the heart of many chemical processes in nature. The pathway and dynamics of the ring opening of a model heterocycle have now been investigated by femtosecond photoelectron spectroscopy combined with ab initio theory, enabling the visualization of rich dynamics in both the ground and excited electronic states.

White phosphorus (P₄) is very reactive but is relatively difficult to activate without relying on transition metals. Now, it has been shown that the degradation of P₄ can be mediated by two divalent silicon atoms in a bis(silylene) scaffold to give a diphosphorus complex that can be further functionalized and also act as a P⁻ transfer agent.

Patterns formed by artificial out-of-equilibrium chemical oscillating networks (such as the Belousov–Zhabotinsky reaction) are difficult to control with any precision. Now, it has been shown that low-intensity audible sound can be used to generate spatiotemporal patterns with a programmable distribution of redox- and pH-responsive chemical systems and supramolecular assemblies in solution.

Artificial intrinsically disordered proteins (A-IDPs) have now been shown to form exclusionary, intracellular droplets that can be designed using simple principles that are based on the aromatic/aliphatic ratio and molecular weight. Droplets that sequester an enzyme and modulate enzyme efficiency on the basis of the molecular weight of the A-IDPs were also engineered using A-IDPs as a minimal condensate scaffold.

Chemical reactions usually proceed through either a radical, concerted or ionic mechanism; transformations in which all three mechanisms occur are rare. Now, the mechanical dissociation of an N-heterocyclic carbene precursor has been shown to proceed with the rupture of a C–C bond through concomitant heterolytic, concerted and homolytic pathways.

Visualization of endogenous G-quadruplexes (G4s) in living cells by fluorescence microscopy has been hampered by the high concentrations of G4-binding probes required, which can artificially induce additional G4 formation. Now, a G4-specific fluorescent probe (SiR-PyPDS) has been developed that enables single-molecule and real-time detection of individual G4 structures in living cells without perturbing G4 formation and dynamics.

Access to both enantiomers of a chiral target compound typically relies on reversing the absolute configuration of the chiral component in the reaction system that is used to make them. A time-dependent enantiodivergent synthesis is reported in which the same enantiomer of a chiral catalyst can give both enantiomers of the product, depending on the reaction time.

Molecular rotors have been engineered within the bicyclopentane–dicarboxylate struts of a metal–organic framework—the bicyclic unit is the rotator and the carboxylate groups serve as the stator. In a zinc-based metal–organic framework, the crossed conformation of the strut–metal nodes enables fast rotation of the bicyclic moiety, but in the corresponding zirconium metal–organic framework a change in the conformation results in much slower rotation.

Multivalent binding is a common strategy to enhance the interactions between weak binding partners. Now, following this principle, DNA origami scaffolds have been used to arrange DNA aptamers into specific geometries and to optimize linker spacings and flexibilities, which results in artificial binding sites with very high affinities for their corresponding ligands.

Using readily accessible tropones and γ-methylidene-δ-valerolactones, the divergent synthesis of three classes of challenging [5.5.0] or [4.4.1] bicyclic systems has been achieved—with high efficiency and stereoselectivity—through Pd-catalysed higher-order cycloaddition. Mechanistic studies and density functional theory calculations indicate that the divergent reactions arise from the different reactivity of two diastereomeric intermediates.

The biosynthesis of goadvionins—hybrid lipopeptide antibiotics—is not fully understood. An unusual acyltransferase, GdvG, has now been identified and shown to catalyse a condensation reaction between an acyl-carrier-protein-tethered very-long-chain fatty acid and an eight-residue ribosomally synthesized and post-translationally modified peptide. The position of functional groups in the very-long acyl chain have been determined by tandem mass spectrometry.