Chiral amines can be made by insertion of a carbene into an N–H bond followed by asymmetric protonation, but these steps typically require two different catalysts. Now, a team led by Frances H. Arnold, Kai Chen and Marc Garcia-Borràs has shown that it is possible to engineer dual-function enzymes in which a single active site can catalyse carbene N–H insertion and proton transfer to form α-amino lactones with high enantioselectivity. The image on the cover of this issue depicts a stylized representation of one of the cytochrome P450 enzymes developed in this study.

See Liu et al

Ribozymes — catalytic RNA structures — require optimal salt compositions and concentrations to function correctly. Although several origin-of-life theories propose key roles for ribozymes in the emergence of life, it is unclear what mechanisms could have maintained the required salt environments on the early Earth. Now, a team led by Hannes Mutschler and Christof Mast has shown that salt solutions obtained from leaching basalt inhibit ribozyme function, but that heat flow across rock fissures changes both the absolute concentrations and the concentration ratios of different salts, enabling catalysis. The cover image for this issue shows an artistic representation of a ribozyme on a basalt rock.

See Matreux et al.

The separation of ethylene and ethane is an important, but currently energy-intensive, industrial process. Now, Banglin Chen and co-workers have assembled a microporous hydrogen-bonded organic framework (HOF) that exhibits very good selectivity for adsorbing ethylene over ethane through a gating mechanism. The HOF (as depicted on the cover) consists of tetracyanobicarbazole building blocks held together by C–N•••H–C hydrogen bonds and is stable under harsh conditions. It produces high-purity ethylene in a fixed-bed column at 333 K — a temperature close to that of real gas mixture streams in practical processes.

See Yang et al.

Although carbenes form exceptionally robust and well-ordered functional monolayers on metal substrates, their assembly on semiconductor surfaces poses a challenge. Now, a team led by Frank Glorius, Norbert Esser and Mario Dähne has demonstrated the formation of thermally stable, well-ordered monolayers of N-heterocyclic carbenes (NHC) on silicon: the material of choice for current semiconductor technology. The cover of this issue depicts NHC adsorption on a silicon substrate by formation of direct bonds to surface adatoms.

See Franz et al.

On-surface polymerizations are often thermally activated and typically yield relatively small polymers with high defect densities. Now, Markus Lackinger and co-workers have used a photo-induced topochemical cycloaddition to covalently crosslink three-bladed anthracene triptycene (fantrip) molecules self-assembled on an alkane-passivated graphite surface. This method produces single-crystalline 2D polymers with domain sizes up to 400 nm. Characterization by in-situ scanning tunnelling microscopy (one such image is shown on the cover) distinguishes between supramolecular and covalent linkages.

SeeGrossmann et al

The functions of DNA G-quadruplexes (G4) are linked to the proteins they interact with; however, it is challenging to identify G4–protein interactions in living cells. Now, a team led by Shankar Balasubramanian has used a chemical proteomics strategy that enables the systematic and unbiased mapping of the DNA G4 interactome in live cells. The image on the cover depicts functionalized G4 ligands that bind endogenous DNA G4s. Photoactivation and cross-linking to G4-interacting-proteins in situ enables these proteins to be separated and subsequently identified.

See Zhang et al

Molecular catalysts can offer several benefits over heterogeneous systems, such as better selectivity, but they typically suffer from stability issues. Now, David Tilley and co-workers have developed a method by which molecular electrocatalysts can reversibly bind to electrode surfaces through host–guest complexation with surface-anchored cyclodextrins — an artistic representation is featured on the cover of this issue. This approach enables desorbed or degraded guest molecules to be replaced with fresh guest molecules, extending the lifetime of the catalytic surface.

See Sévery et al.

Adding two groups to C60 through Bingel cyclopropanation can lead to the formation of many different isomers that can be challenging to separate. Now, using a supramolecular masking approach that relies on the formation of a three-shell complex reminiscent of the concept of Russian dolls, Xavi Ribas, Max von Delius and co-workers have shown that it is possible to selectively form the trans-3 fullerene bis-adduct. As shown on the cover of this issue, the C60 is encircled by a cycloparaphenylene nanohoop which, in turn, is encapsulated inside a self-assembled metal–organic nanocapsule, ensuring that bis-functionalization of the fullerene occurs only at accessible sites to give a single isomeric product.

See Ubasart et al.

The ubiquitous interface between water and other phases provides a unique environment where various important processes take place. For example, chemical reactions occurring at the water interface are important in biological and environmental settings and also in organic/inorganic chemistry and electrochemistry. Now, ultrafast phase-sensitive interface-selective vibrational spectroscopy has revealed that the photoionization reaction of phenol proceeds four orders of magnitude faster at the water surface than in the bulk aqueous phase. The cover shows a representation of the experiment, showing the UV, visible and IR light pulses used to monitor the photochemical change at the air–water interface.

See Kusaka et al.

The shape of a chemical compound is a major factor in its physical and biological properties, but it can be difficult to study conformations other than those with the lowest energy. Now, by incorporating dominant rotors into peptide-based macrocycles, Andrei Yudin and co-workers have been able to explore what they refer to as the 'dark conformational space' of these structures and have observed unusual conformations in which amino acids are forced to adopt rare turn motifs. The cover image shows a collection of macrocycles in which the dominant rotors are illuminated and the blue lines suggest the transmission of strain across the molecules.

See Diaz et al.

The weaving of ligand strands offers the potential for accessing new molecular knots and woven materials. Now, David Leigh and co-workers report the discovery of a combination of anion and metal-ion templates that enables the one-step assembly of a 3 × 3 interwoven grid that is an intermediate in the synthesis of an endless (74) knot. The endless knot is a basic motif of Celtic knotting, it is one of the eight auspicious symbols (the Ashtamangala) — where it represents the union of wisdom and method — and is also the smallest Chinese knot. A schematic representation of the knot is shown on the cover of this month’s issue, February 2021, which marks the start of the Chinese Year of the Ox — Xīnnián kuàilè!

See Leigh et al.

Photoinduced charge-transfer can lead to various important and interesting phenomena, such as magnetism, ferroelectricity and photocatalysis. However, an atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin-transition, is still under debate because of the speed at which it occurs. Now, a team led by Eric Collet and Marco Cammarata have used femtosecond X-ray spectroscopy to reveal how photomagnetism emerges in cyanide-bridged CoFe coordination networks. They see that it is the spin-transition on the cobalt atom, occurring within ~50 fs, that drives the subsequent electron transfer from Fe (red) to Co (blue) within 200 fs.

See Collet et al.