Volume 7 Issue 10, October 2015

Spin-triplet excitations commonly migrate through direct electron exchange between neighbouring molecules. Now, experiments show that back-and-forth interconversion between spin-triplet and spin-singlet states can significantly speed up triplet migration in organic crystals.

A patterned, spatially resolved gel has now been devised. The two-component gel is formed by sequential assembly of two independent networks of fibres, and the subsequent selective removal of one network by irradiation.

A method for directly probing binding interactions in free solution, without the need for chemical tagging, offers exciting opportunities for non-perturbative analyses of biomolecules in their native state.

Nanocrystals with precisely defined structures offer promise as components of advanced materials yet they are challenging to create. Now, a nanocrystal made up of seven cadmium and twelve chloride ions has been synthesized via a biotemplating approach that uses a de novo designed protein.

Vinyl polymers are appealing materials owing to their ease of synthesis and broad diversity. Their carbon–carbon backbones resist degradation, however, which limits the applications for which they can be used. This Review Article considers the most promising approaches to the design of degradable vinyl polymers and discusses the potential of these materials for biomedical applications.

Understanding the interplay between singlet fission and exciton transport is important if singlet-fission materials are to be used for solar cell applications. Now, a cooperative singlet–triplet transport mechanism has been revealed through ultrafast transient absorption microscopy.

The question of how divalent metal ions direct the folding of ribozymes is a major unsolved problem. A computational model has now been used to reveal the molecular mechanism by which Mg²⁺ drives the Azoarcus ribozyme into a catalytically functional state. Simulations also show that although Ca²⁺ drives folding it leaves the active site unstable.

Labelling biomolecules to improve the sensitivity of analysis can perturb their interactions. Now, microfluidic and chemical tools have been used to allow simple, sensitive detection of a labelled system to reveal the behaviour of the native and physiologically relevant unlabelled system. The system was used to characterize the solution-phase behaviour of a clinically relevant protein–protein interaction.

Regioselective epoxide opening of an enantiopure epoxy–alkyne results in the stereospecific introduction of functional side-chains into growing macromolecules. This process—in combination with 'click' chemistry and orthogonal deprotection of terminal alkynes—underpins an iterative exponential growth methodology that enables the efficient synthesis of >6-kDa stereo- and sequence-controlled polymers.

Cyclohexa-2,5-dien-1-yl groups bound to silicon act as masked Si–H bonds that can be released by the action of tris(pentafluorophenyl)borane (B(C₆F₅)₃). In this way, hazardous SiH₄ is unleashed from appropriately substituted precursors and engages in alkene hydrosilylation promoted by the same boron catalyst. The overall process is a transfer hydrosilylation of alkenes with monosilane.

Protein PEGylation is routinely used to produce molecules with improved pharmacokinetic properties. However, despite their importance, the structure of PEGylated proteins has remained elusive. Now, the first crystal structure of a model β-sheet protein modified with a single PEG chain has been reported. NMR spectroscopy data indicates that the protein and PEG behave as independent domains.

The late-stage functionalization of unactivated C(sp³)−H bonds could be useful for the rapid development of structure–activity relationships, but highly target-specific conditions make it challenging. Now, a strategy for the preparation of a variety of β-functionalized alcohol derivatives through a site-selective C−H sulfonyloxylation and subsequent S_N2 reactions is described.

A cascade reaction network has been created that can function in a manner that is superficially similar to the most basic steps of the vertebrate adaptive immune response. This reaction network uses DNA and enzymes as simple artificial analogues of the components of the acquired immune system.

Catalysis with N-heterocyclic carbenes produces diverse outcomes depending on which of the many possible reaction mechanisms dominates. Control of this reactivity within a single reaction type has rarely been demonstrated. Now, starting from identical substrates, a switchable catalytic activation is shown to afford different products with high regio- and stereoselectivity.

Multicomponent supramolecular hydrogels have been prepared using a self-sorting mixture of two different gelators—one of which is photosensitive. Irradiation of the gels through a mask leads to the photosensitive network being selectively removed by a light-triggered gel-to-sol transition in a process that can be used to produce patterned gels with spatially controlled properties.

Giovanni Baccolo relates tales of tantalum, an element known, and named, for its inertness, yet one that holds some surprises, such as a naturally occurring nuclear isomer.