Articles in 2021

The specificity of human and animal viruses that engage with O-acetylated sialic acids has now been probed using a collection of O-acetylated sialoglycans obtained by diversification of trisaccharide precursors with viral haemagglutinin–esterases. The results revealed host-specific patterns of receptor recognition and showed that human respiratory viruses uniquely employ 9-O-acetylated α2,8-linked disialosides as receptors.

Redox mediators are important for improving the rechargeability of metal–air batteries, however, how they affect singlet oxygen formation and hence parasitic chemistry is unclear, hindering strategies for their improvement. Now, the mechanism of mediated peroxide and superoxide oxidation is elucidated, explaining how redox mediators either enhance or suppress singlet oxygen formation.

The post-translational modification O-GlcNAc on amyloid-forming proteins can inhibit their aggregation. Now, it has been shown that O-GlcNAc modification of small heat shock proteins HSP27, αA- and αB-crystallin can increase their anti-amyloid activity and block the amyloid formation of both α-synuclein and Aβ(1–42). A mechanism for this protective effect based on decreased physical interactions is also proposed.

Analysis of the thermodynamics of protein–N-glycan interactions perturbed by mutations has revealed an enthalpy–entropy compensation that depends on the electronics of the interacting side chains. Machine-learned and statistical models showed that protein–N-glycan interactions highly correlate with stereoelectronic effects, and that a major part of protein–N-glycan interactions can be explained using the energetic rules of frontier molecular orbital interactions.

A reagentless method for detecting analytes based on the motion of an inverted molecular pendulum has now been developed. The sensor is capable of detecting important physiological markers of stress, allergy, cardiovascular health, inflammation and cancer and works in blood, saliva, urine, tears and sweat. The sensor is also capable of collecting data in living animals.

The metathesis of carbon–carbon double bonds is an important tool in organic synthesis and now a similar reshuffling has been carried out with heavier alkene analogues featuring unsymmetrically substituted Ge=Ge double bonds. This reaction enables the synthesis of symmetric molecular digermenes as well as a polymer based on Ge=Ge repeat units.

Enzymatic reactions involving mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in synthetic transition-metal catalysed reactions. Now, it has been shown that zinc-containing carbonic anhydrase enzymes can catalyse hydride transfers from silanes to ketones with high enantioselectivity and there is evidence to support the intermediacy of a mononuclear zinc hydride.

It is difficult to investigate the chemical properties of superheavy elements, which are only available an atom at a time and rapidly decay. A co-precipitation method with samarium has now been developed that suggests rutherfordium would form hydroxide precipitates—but not ammine ones—if it were possible to perform these experiments on macroscopic quantities.

A metal–organic framework (MOF) has been prepared that features dynamic rotors embedded within its crystalline lattice. The dipolar F₂-functionalized carboxylate linkers—rapidly rotating at room temperature—show correlated behaviour upon cooling, converting the paraelectric MOF into an ordered antiferroelectric one below 100 K.

Constrained molecules typically adopt one major conformation and this limitation prevents the study of other energetically less-favourable conformations. Nevertheless, these alternate structures might prove to be useful and it has now been shown that a dominant rotor method can alter the energetic landscape of peptides to create two-well systems with distinct conformational behaviour.

Some metal–organic frameworks (MOFs) can promote photocatalytic hydrogen evolution and others can facilitate water oxidation, but it is difficult to combine them into a single system. Now, by confining MOFs that can promote each half-reaction within the hydrophobic and hydrophilic regions of a liposome to avoid the fast recombination of photo-generated charges, evidence for water splitting has been obtained.

Collagen-like peptides can self-assemble into hundreds of closely related triple helices. Now, an algorithm has been developed that predicts the most stable helix and the extent to which it will assemble to the exclusion of the competing helices. This information can help improve the understanding of triple helix design and assembly.

Solvent plays a critical role in electron-transfer reactions, but short-range solvation dynamics are challenging to observe. Now, femtosecond X-ray solution scattering has been used to directly monitor the reorganization of water upon ultrafast intramolecular electron transfer in a bimetallic complex. Coherent motions of the first-shell water molecules are observed, arising from changes in solute–solvent hydrogen bonding.

Reactions at the interface between water and other phases play important roles in various chemical settings. Now, ultrafast phase-sensitive interface-selective vibrational spectroscopy has revealed that the photoionization of phenol can occur four orders of magnitude faster at the water surface than in the bulk aqueous phase.

A de novo designed zinc-binding protein has been converted into a highly active, stereoselective catalyst for a hetero-Diels–Alder reaction. Design and directed evolution were used to effectively harness Lewis acid catalysis and create an enzyme more proficient than other reported Diels–Alderases.

In an effort to extend the important hydroformylation reaction, a palladium-catalysed carboformylation reaction has now been developed in which two new carbon–carbon bonds are created across an alkyne. This modular reaction relies on a CO shuffling process and uses an acid chloride as a dual carbon and CO source.

Stimuli-responsive control of drug activation can mitigate issues caused by poor drug selectivity. Now, it has been shown that mechanical force—induced by ultrasound—can be used to activate drugs in three different systems. This approach has enabled the activation of antibiotics or a cytotoxic anticancer agent from synthetic polymers, polyaptamers and nanoparticle assemblies.

The synthesis of a zigzag carbon nanobelt has been achieved through an iterative Diels–Alder reaction followed by reductive aromatization. The isolated nanobelt was fully characterized by X-ray crystallography and its wide energy gap with blue fluorescence properties was revealed by photophysical measurements.

Iron-catalysed [2+2] cycloaddition/oligomerization of neat butadiene affords (1,n′-divinyl)oligocyclobutane—a telechelic, crystalline material consisting of 1,3-enchained cyclobutyl units. This oligocyclobutane can be chemically recycled to pure butadiene using the same iron catalyst employed in its synthesis, demonstrating design principles for next-generation plastic materials that can be returned to pristine monomer.

Recent experiments reporting the isomerization of CO on a NaCl(100) surface—from C adsorbed to O adsorbed—represent a major challenge to simulate from first principles. Now, using dynamics calculations and (CO–NaCl)_n cluster models that feature CO–CO interactions, it is found that isomerization occurs via a ‘roaming’ mechanism at a large distance from the NaCl(100) surface.