Articles in 2016

Nature has evolved a variety of different mechanisms to generate chemical diversity; however, the reactions responsible for generating such diverse chemical libraries are often not clear. Now, the mechanisms employed by entomopathogenic bacteria for the biosynthesis of a large family of bioactive peptides have been identified. These include substrate promiscuity, enzyme cross-talk and enzyme stoichiometry.

A computational method to design cyclic protein homo-oligomers has been developed. Using this approach, a series of idealized repeat proteins incorporating designed interfaces that direct their assembly into complexes possessing cyclic symmetry were fabricated. 15 out of 96 oligomers that were characterized experimentally were shown to be consistent with the computational model.

Methods utilizing renewable feedstocks are critical to accessing molecules of industrial importance in light of the present ecological and economic climate. Here, it is shown that umpolung reactivity of carbonyl compounds can be used for nucleophilic additions to yield a diverse array of valuable alcohols as an alternative to using stoichiometric organometallic reagents.

Polytheonamides are giant peptide toxins produced by the uncultivated sponge bacterium Entotheonella factor. The biosynthesis of polytheonamides involves up to 50 post-translational modifications. Now, heterologous expression in Escherichia coli and Rhizobium hosts have shown that a minimalistic, iterative enzyme set introduces this exceptional molecular complexity via epimerizations, C-/N-methylations, hydroxylations, dehydration and proteolytic maturation.

The direct transfer of primary amino and hydroxyl groups to arylmetals in a scalable and environmentally friendly fashion remains a formidable synthetic challenge. Here, it is demonstrated that bench-stable N–H and N–alkyl oxaziridines can be used as efficient multifunctional reagents, without deprotonation, for the direct primary amination and hydroxylation of (hetero)arylmetals.

Aggregation usually prevents dissolution of graphene in water. Now, hydroxide ion adsorption has been shown to allow the stabilization of true single-layer graphene in water — with no surfactant required — so long as the liquid is degassed beforehand. The resulting aqueous dispersions can contain high concentrations of exfoliated graphene that are stable for several months.

Homogeneous crystal nucleation has now been observed by transmission electron microscopy in real time on a molecular scale. Countercation-dependent observations of polyoxometalate proto-crystal formation confirm existence of a higher energy classical molecular attachment mechanism, as well as a lower energy two-step mechanism via an intermediate dense phase.

Discovered during secret testing by the United States, Joanne Redfern tells us about element 99 and why its namesake cautioned against the very technology that led to its creation.

Three different methods that use a single ruthenium catalyst to enable the facile formation of meta- and para-substituted alkenylarenes have now been developed. The reactions proceed through a tandem alkenylation/decarboxylation process and provide several advantages over alternative approaches.

Despite their potential as drugs, peptides are generally not cell permeable, which limits their practical applications in medicine. Now, linear peptides have been cyclized by using a heteroaromatic linker. This cyclization both improves passive membrane permeability and stabilizes a biologically relevant secondary structure.

The targeted release of bioactive molecules to diseased tissues has the potential to improve therapeutic efficacy, but not all drugs contain a free functional group that can be easily attached to an antibody. Now, a linker technology has been developed to enable the traceless release of tertiary and heteroaryl amine-containing drugs.

No longer a theoretical dream, this Perspective describes effects of oriented external electric fields on rates and selectivity patterns of nonpolar reactions. Discussions of the Diels–Alder reaction, C–H and C=C bond activations and so on, underscore the potential usage of oriented electric fields as future smart catalysts, inhibitors and reagents in chemistry.

Flat, prochiral molecules form chiral adsorbates on achiral surfaces, but such assemblies are globally racemic. Now, it is shown that this mirror symmetry can be broken through stereocontrolled on-surface synthesis. Enantiopure helicene molecules can be transformed into flat, enantiofacially adsorbed products through a cascade of reactions on Ag(111) monitored by high-resolution scanning probe microscopy.

Isolating nanoscale species in liquids permits their scalable manipulation, enabling numerous fundamental and applied processes. Thus, achieving true dissolution of 2D materials is particularly desirable. Now, ionic salts of a range of important layered materials have been shown to spontaneously dissolve, yielding solutions of charged, monodisperse, undamaged and easy-to-manipulate 2D nanosheets.

Although ribose aminooxazoline has been shown to be a potential intermediate in prebiotic pyrimidine ribonucleotide synthesis, a route by which this could occur has remained elusive. Now, a remarkably efficient photoanomerization reaction has been investigated by theory and experiment. The new route affords enantiomerically pure ribonucleotides when the starting material is enantioenriched.

Anti-proliferative compounds that display enhanced toxicity in a low-oxygen (hypoxic) environment may be used to eradicate aggressive and therapy-resistant cancer cells. Now, a promising lead structure has been identified in the BE-43547-class of depsipeptide natural products.

Porous molecular crystals have desirable properties, but are hard to form with the level of structural control seen for extended framework materials. Now, a ‘mix-and-match’ chiral recognition strategy has been used to form reticular porous supramolecular nanotubes and 3D networks, providing a blueprint for pore design in molecular crystals.

The assembly of transmembrane barrels formed from short synthetic peptides has not been previously demonstrated. Now, a transmembrane pore has been fabricated via the self-assembly of peptides. The 35-amino-acid α-helical peptides are based on the C-terminal D4 domain of the Escherichia coli polysaccharide transporter Wza.

Methods for preparing enantiomerically enriched products are often dependent on the structure of a catalyst. Here, it is shown that a self-amplifying catalyst is able to ‘sense’ the chirality of the catalytic product and induce enantioselectivity. Flexible ligand and product interaction sites are key to the increasing enantioselectivity over the course of the reaction.