Articles in 2012

Templated atomic layer deposition (ALD) is used to create oxide ‘nanocavities’ on the surface of catalyst particles. Subnanometre-nm films containing nanocavities act as sieves for the underlying catalyst, resulting in high selectivities for the smaller of two reactants in competitive oxidations or reductions.

Efficient hydrogen-evolving catalysts comprising readily available elements are needed if hydrogen is to be adopted as a clean alternative to fossil fuels. Now, a diimine–dioxime cobalt complex has been covalently attached to a carbon nanotube electrode to yield an active and robust electrocatalyst for hydrogen generation (55,000 turnovers in seven hours) from aqueous solutions.

Methods that fix atmospheric nitrogen to ammonia under mild conditions could offer a more environmentally benign alternative to the Haber–Bosch process. Now, a Ru-loaded electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄, is reported that acts as an efficient electron donor and reversible hydrogen store, and is demonstrated to function as an efficient catalyst for ammonia synthesis.

RNA compartmentalization is essential for cellular functions and may have played a pivotal role in the emergence of life. However, the consequences of compartmentalization on RNA catalysis have been largely unexplored. Here, partitioning of catalytic RNA in a two-phase aqueous polymer solution increased local RNA concentration, enhancing ribozyme kinetics.

A short-lived diiron–oxo species — based on a nitrido-bridged bis-porphyrin 1 1platform — capable of efficiently oxidizing the strongest of C–H bonds has been prepared and spectroscopically characterized. The catalytic properties of this high-valent diiron(IV)–oxo complex were elucidated by studying the oxidation kinetics of a range of alkanes.

Aspartic acid-based catalysts that are selective for oxidation of either the 2,3 position or the 6,7 position of certain isoprenols have been discovered. The catalysts emerged from a diversity-based approach employing the one-bead-one-compound libraries. The site-selectivity of the catalysis seems to derive from the hydroxyl group in the substrate, although the details of this are not yet known.

Single-molecule experiments reveal substantial molecule-to-molecule variation in the Mg²⁺-induced isomerization dynamics of Holliday junctions (HJs). Effective ergodicity breaking of time trajectories results in the partitioning of HJ dynamics into multiple clusters. The observed dynamical heterogeneity is a consequence of various internal multiloop conformations that are frozen by Mg²⁺ ions.

Heterogeneous catalysts are generally more readily recycled than homogeneous catalysts, but the latter are more easily modified to tune reactivity and selectivity. Here, the dendrimer coating of gold nanoparticle catalysts is shown to be a surrogate for the ligands of homogeneous catalysts. Tuning of product distribution and reaction selectivity is possible when these catalysts are employed in a fixed-bed flow reactor.

A demonstration of simple sugar synthesis from single carbon feedstocks would provide significant support for the involvement of RNA in the origin of life. Here, hydrogen cyanide is shown to feed a cyanocuprate photoredox cycle that ultimately provides both the starting material and the reducing power necessary for a Killiani–Fischer-type sugar synthesis.

Life-science research and biomedical diagnostics call for robust fluorescence barcodes of compact size and high multiplexing capability. Here DNA-origami technology was used to construct a new kind of geometrically encoded barcode with excellent structural stiffness. They hold promise for both in situ and ex situ imaging of diverse biologically relevant entities.

Visible-light-mediated photocatalytic generation of carbon-centred radicals from alkyl, alkenyl and aryl iodides, which then undergo subsequent hydrogen-atom abstraction or reductive cyclizations, is reported. The protocol is characterized by the use of inexpensive reagents, mild conditions, exceptional functional group tolerance, and good to high yields.

Sesquiterpenes are biosynthesized from linear isoprenols through the intermediacy of multiple, high-energy carbocations. Here a strategy is demonstrated for mimicking these reactions in bulk solvent to yield strained, acid-labile terpenes. Key to the success of these reactions is the sequestration of the counteranion away from the reactive carbocation, a strategy that should enable further study of challenging polycyclizations.

Porous solids are well suited to the capture of environmentally harmful gases, but further understanding of the solid–gas interactions involved is required. Combining dynamic and static characterization with modelling, researchers have now described how a metal–organic framework binds CO₂ and SO₂ selectively through hydroxyl groups — rather than amine ones as typically featured.

Representing the first successful rational reprogramming of function in a de novo protein, the reactivity of a designed di-iron carboxylate protein from the Due Ferri family was altered from hydroquinone oxidation to arylamine N-hydroxylation through the introduction of a critical third histidine ligand in the active site.

Bistable materials, which exist in either one of two phases under identical conditions, are intriguing both from a fundamental perspective and for their practical applications. A cyanide-bridged [CoFe] coordination chain has now been prepared that shows both magnetic and electric bistabilities in the same temperature range, undergoing thermo- and photo-induced conversions between insulating, semiconducting and single-chain magnet-type phases.

Arylpyrrolidino amidothiourea catalysts are shown to catalyse the enantioselective ring-opening of episulfonium ions by indole derivatives. Catalysis and enantioinduction are achieved by selective transition-state stabilization of the major pathway in the rate- and selectivity-determining step through a network of attractive anion-binding, cation–π and hydrogen-bonding interactions between the catalyst and the reacting partners.

A family of robust β-sheet macrocycles that can display a variety of heptapeptide sequences from different amyloid proteins is introduced. These amyloid β-sheet mimics can be tailored to antagonize aggregation of the proteins, thereby reducing the toxicity associated with diseases such as Alzheimer's.

Rapid diagnostic methods that can be applied in resource-limited settings are important in the fight against tuberculosis. Here, fluorogenic probes are described that are activated by BlaC — an enzyme secreted by tubercle bacilli. The probes have enabled detection in unprocessed human sputum of live pathogen in less than 10 min.

So far, reports of molecular electrochemical water oxidation have involved catalytic transition metal complexes. Now it is demonstrated that water can be oxidized, and oxygen evolved, using a simple organic, flavin derivative.

Many biological processes involve the binding of proteins to cell membrane receptors, making these proteins valuable disease biomarkers and therapeutic targets. A label-free plasmonic microscopy method has now been devised to determine the distribution and local binding kinetics of these ‘membrane proteins’, on the surface of single living cells rather than ex situ.