Volume 8 Issue 5, May 2016

A trio of recent discoveries in physics should be celebrated by everyone, even chemists, argues Bruce Gibb.

Understanding the minute details of CO₂ transport is key to finding new technologies that reduce the hazardous levels of CO₂ in our atmosphere. Now, the observation that the transport of CO₂ in molten calcium carbonate occurs faster than standard molecular diffusion brings us one step closer.

A fundamental challenge in systems chemistry is to engineer the emergence of complex behaviour. The collective structures of metal cyanide chains have now been interpreted in the same manner as the myriad of magnetic phases displayed by frustrated spin systems, highlighting a symbiotic approach between systems chemistry and magnetism.

A chiral [2]rotaxane in which the asymmetry is derived from the way in which the two components are mechanically interlocked — rather than being encoded in the covalent connectivity of the components themselves — has been shown to act as an enantioselective organocatalyst.

Chemical protein synthesis can enable the preparation of proteins containing post-translational modifications or unnatural variations such as D-amino acids. Such modified proteins are not easily fabricated by other methods. This Review provides an overview of the current approaches for the chemical synthesis of proteins.

A collaborative approach between experiment and simulation has revealed a single mutation in the F/G loop of the newly described nitrating cytochrome P450 TxtE that controls loop dynamics and, more surprisingly, the regioselectivity of the reaction. This mutation is present in a subset of homologous nitrating P450s that produce a previously unidentified biosynthetic intermediate, 5-nitro-L-tryptophan.

Li⁺-selective solid electrolytes may enable next-generation battery systems, such as Li–S and Li–O₂. Now, in an exemplar system, it is shown that a resistive interphase forms at the interface between solid and liquid electrolytes, termed the solid-liquid electrolyte interphase (SLEI). An in situ study of this undesirable effect is supported by state-of-the-art surface analysis.

Endohedral C₇₀ fullerenes containing either one or two water molecules have now been prepared using a molecular-surgery approach. The structure of H₂O@C₇₀ was determined by single-crystal X-ray analysis, revealing the encapsulated water molecule to be in an off-centre position. In (H₂O)₂@C₇₀, the two water molecules form a discrete dimer held together with a single hydrogen bond.

Competing metallophilic and electrostatic interactions between gold and/or silver cyanide chains govern their assembly into different structures. An analogy has now been drawn between these systems and two-dimensional magnets. Supramolecular interactions between the chains have been tuned to mimic different magnetic interactions, leading to the realization of complex states predicted for magnets.

The development of cells requires a mechanism to support homeostasis—the maintenance of constant internal conditions—as cellular growth results in internal dilution. Now, a simple physical process is described in which short oligonucleotide inhibitors enable dilution-driven activation of encapsulated ribozymes via membrane growth, suggesting homeostatic mechanisms could have existed in the earliest cells.

The solvation behaviour of CO₂ in carbonate melts is important from both a geochemical point of view and with respect to its electroreduction. Now, simulations have shown that solvation of CO₂ in molten CaCO₃ leads to the formation of the pyrocarbonate anion, C₂O₅^2–, which significantly enhances the transport of CO₂ via a Grotthuss-like mechanism.

Capsular polysaccharides are a protective layer enveloping pathogenic bacteria. Understanding their export could guide the design of therapeutics that render bacteria vulnerable to attack by the immune system or other therapeutic agents. Now, a synthetic strategy of polyglycosylation has been developed to obtain defined capsular polysaccharide fragments. Subsequent nanolitre detection enables their export to be studied at the single-molecule level.

Controlling the morphology and composition of hybrid nanostructures is desirable for applications, but it has proven challenging to precisely combine different nucleation sites and growth modes. Now, three types of hierarchical 1D/2D nanostructures have been prepared by selectively growing semiconductor nanorod arrays (CdS or CdSe) on the different facets of hexagonal nanoplates.

Precise control of vesicle size is highly desirable both for basic biochemical research and biomedical applications. Now, monodispersed sub-100-nm vesicles with predefined sizes have been produced using a method based on membrane self-assembly within a DNA-nanostructure guide.

Understanding the correlation between structure and charge transport properties of a DNA-based single molecule device is crucial to the creation of nanoscale functional devices. Now, a DNA-based molecular rectifier with a high rectification ratio has been constructed by site-specific intercalation of small molecules (coralyne) into native double-stranded DNA.

L-Cysteine-derived thiazolidines have now been shown to be artificial substrates of the radical SAM enzyme HydE, which converts them into S-adenosyl-L-cysteine. Carbon–sulfur bonds are formed in a concerted mechanism that involves the formation of a C-centred radical that concomitantly attacks the S atom of a thioether. This is the first example of a radical SAM enzyme that reacts directly on a sulfur atom instead of abstracting an H-atom.

Phase transitions in materials are intriguing, and can also be of practical importance. Below ∼150 K, mixed-valent iron oxide Fe₄O₅ has now been shown to undergo an unusual charge-ordering phase transition that involves the competing formation of iron dimers and trimers, and leads to a significant increase in electrical resistivity.

An important source of atmospheric hydroxyl radicals is from the dissociation of Criegee intermediates produced in alkene ozonolysis reactions. The dissociation dynamics of the prototypical CH₃CHOO Criegee intermediate have now been determined. Complementary experimental and theoretical studies were carried out and the translational and internal energy distributions of the OH radical products were characterized.

From secretive beginnings to serving in missions on Mars, Rebecca J. Abergel and Eric Ansoborlo take a look at the glowing mark curium has left on contemporary science and technology.