Articles in 2011

Optimizing oxygen-reduction and -evolution reactions is crucial for improving fuel cell efficiency, but the reaction is poorly understood at the nanoscopic level. Now, the oxygen activity of a platinum-functionalized surface has been mapped at below 10-nm resolution using electrochemical strain microscopy.

The generation of two-dimensional homochiral porous molecular networks at the liquid–solid interface is described. Using scanning tunnelling microscopy, the formation of homochiral porous networks was observed both from solutions of homochiral molecules and from solutions of achiral molecules in the presence of a small amount of a chiral modifier.

Selective reaction of one C–H bond among many in complex organic molecules is a grand challenge for organic chemistry. Here, starting from an enzyme that oxidizes two positions in a steroid without bias, laboratory evolution is used to prepare mutants that can regio- and stereoselectively oxidize either position.

Membrane-enclosed reaction compartments are considered important for establishing plausible pathways of prebiotic organization. Here, simple mixing of mononucleotides and cationic peptides in water is shown to produce microdroplets that sequester photo-active molecules, catalytic nanoparticles and enzymes. Such droplets might provide plausible pathways of prebiotic organization prior to the emergence of membrane-based compartmentalization on the early Earth.

A drawback of recently reported prebiotic routes to RNA is a requirement for enantioenriched reactants. Here, the presence of a slightly enantioenriched amino acid in the reaction mixture is shown to drive the formation of enantiopure RNA precursors. This provides a plausible scenario in which single-handed biological molecules were formed prior to the emergence of self-replicating informational polymers.

Portable sensors for the rapid quantitation of a variety of analytical targets could revolutionize both medical diagnostics and environmental monitoring. Here, functional DNA sensors that release the enzyme invertase in response to an analyte of choice are described. The enzyme converts sucrose to glucose which can then be easily detected using a widely available personal glucose meter.

Producing methanol — useful as both a fuel and a synthetic building block — from carbon monoxide and carbon dioxide has been achieved using homogeneous catalytic hydrogenation of carbonates, carbamates and formates. The catalyst is a dearomatized ruthenium(II) pincer complex and the reaction proceeds efficiently under mild conditions.

An important goal for the improvement of certain heterogeneous catalysts is to decrease the amount of platinum required while maintaining high catalytic activity. Now, the practical synthesis of a stable catalyst consisting of isolated single platinum atoms anchored onto iron oxide nanocrystallites has been developed that exhibits high activity for CO oxidation.

Rather than tuning metal–ligand interactions using carbon-based substituents, the effect of icosahedral carborane moieties — boron-rich clusters — on the coordination chemistry of phosphine–thioether ligands has been investigated. Depending on the positional attachment of the sulfur atom, the carboranes acted as either strong electron-withdrawing or strong electron-donating substituents.

Acyclic azomethine imines would be useful prochiral electrophiles in catalytic asymmetric reactions, but their generation often requires harsh conditions. Here, they are generated under mild conditions in the presence of an axially chiral dicarboxylic acid, with the chiral counterion (the conjugate base) then directing an enantioselective reaction with a diazoacetate nucleophile.

Enzymes are capable of modifying complex organic structures with exquisite selectivity. Understanding these processes could help in the development and production of new bioactive compounds. Here, a complete reconstitution of tailoring steps in tirandamycin biosynthesis shows that two enzymes repeatedly exchange substrates to achieve several different oxidations en route to this family of antibiotic compounds.

A long-standing problem with the RNA-world hypothesis is that enzyme-free replication of RNA strands has not been demonstrated. Here, immobilization of a template strand and periodic replacement of a solution containing activated nucleotides allows the copying of unmodified RNA sequences containing any of the four natural nucleobases in near-quantitative yield.

Multiple specific binding interactions have typically been created from DNA using Watson–Crick complementarity. Now, diverse bonds have also been obtained through the geometric arrangement of blunt-end stacking interactions. Two approaches to specific interactions — binary and shape coding — are demonstrated. The thermodynamics and binding rules of the resulting ‘stacking bonds’ are explored.

Oligosaccharides displayed at cell surfaces have important biological functions — such as controlling the entry of viruses — but a full understanding of this behaviour requires the synthesis of such compounds, which remains challenging. Here, two synthetic octasaccharides were shown to have remarkably similar inhibition of herpes simplex virus type 1 infection of cell cultures to the natural oligosaccharide identified in enzymatic studies.

Nitrenium salts have been known for more than 100 years. Despite being isoelectronic and isostructural to the ubiquitous N-heterocyclic carbene ligands and other main-group analogues, their coordination to metals has remained elusive. Here, the first examples of nitrenium ions as ligands for transition metals are described, along with investigations of their electronic properties.

Loline is a small alkaloid with a deceptively simple-looking structure. Here, a remarkably short synthesis is reported, the key step of which is a transannular aminobromination. The synthesis provides access to loline and to several other members of the loline family in sufficient yield to support a programme investigating the complex biological interactions of these compounds.

The daphnane diterpene orthoesters constitute a structurally fascinating family of natural products that exhibit remarkable and potent biological activities. A gateway strategy designed to provide general synthetic access to and biological evaluation of natural and non-natural daphnanes is described and used for yuanhuapin analogues.

Differential cross sections for the rotationally inelastic scattering of NO by Ar are reported with unprecedented quantum-state resolution. The experiments give important details about the mechanism of this fundamental collisional process, providing evidence for a parity-dependent quantum-mechanical interference effect.

With the cost of noble metal oxygen-reduction catalysts rendering some fuel cells and batteries prohibitively expensive, the search for effective and cheaper catalysts is underway and would be speeded up by ‘design principles’. Now, the catalytic activity of oxide materials has been correlated to σ*-orbital occupation and the extent of metal–oxygen covalency.

In extended networks, light-induced magnetic ordering through spin change typically involves a charge-transfer mechanism, and thus a valence change of the magnetic metal centres. Now, such long-range ordering has been achieved in a three-dimensional metal–organic framework through the low-spin to high-spin transition of iron(II) centres, leading to a pronounced spontaneous magnetization.