Volume 2 Issue 12, December 2010

Michelle Francl wonders just what we're buying — and buying into — when we shop for our laboratories.

Enzymes keep their catalytic reactivity under fine control, letting appropriate molecules approach their active sites to perform reactions. Now, studies of calixarenes attached to gold clusters to emulate this behaviour in synthetic systems suggest that the key to accessibility could be a matter of the relative sizes of ligands and metal clusters.

Testing for enzymes is important for diagnosing various medical conditions but can be problematic because of the complexity of physiological media such as blood. Now, a method of detecting phospholipases has been developed that neatly couples their concentration with the aggregation of gold nanoparticles.

An organocatalytic method for constructing biaryls joins an increasing number of articles reporting metal-free analogues to reactions that traditionally have required a transition-metal catalyst. What does it take to prove that metal is not involved, and does it really matter?

Self-assembly typically occurs through reversible interactions that slowly arrange building blocks into the most thermodynamically favoured structure. The involvement of enzymatic catalysis in the process has now enabled the rapid construction of a variety of low-defect architectures.

The annual Bürgenstock conference brings together a select band of chemists to talk about the many different facets of stereochemistry, and the unique format of the meeting encourages plenty of discussion and debate alongside the traditional lectures and poster presentations.

Chemically derived graphene oxide (GO) has recently moved on from simply being a graphene precursor to attracting interest for its own properties. This Review discusses how the presence of oxygenated groups and domains of sp²- and sp³-hybridized carbons makes GO tunable and promising for various physical and biological applications.

An optical molecular imaging dye is described that is based on an interlocked squaraine rotaxane peroxide. These fluorescent and chemiluminescent dye molecules can be stored indefinitely at low temperature, but on warming to body temperature they undergo a unimolecular reaction, emitting near-infrared light that can pass through a living mouse.

The co-existence of superconductivity and magnetism in single compounds is rare, and heterostructures containing both properties have only been made with complex techniques. Now, a molecular-building-block approach has been applied to match organic and inorganic layers to produce multifunctional materials.

Supramolecular gels based on small-molecule gelators have been shown to be effective media for the growth of organic crystals, including pharmaceutical compounds. Moreover, the gel-to-sol transition can be triggered by molecular recognition with anions, thereby enabling facile recovery of the crystals.

C–H activation has usually been achieved by transition metal-mediated pathways. Here, a cross-coupling between aryl halides and common arenes mediated by 1,10-phenanthroline as catalyst, in the presence of potassium tert-butoxide as base is described. Such reactions open a new window for achieving C–H activation without the need for transition metal catalysts.

DNA has been used as a building block to make a wide variety of molecular architectures, but it remains difficult to make functional structures from this particular construction material. Now, a strategy for the assembly of hybrid RNA–DNA nanostructures has been described, which offers the possibility of combining the programmability of DNA with the rich functionality of RNA.

Uranium oxo groups are very inert, in contrast with many transition metal oxo compounds that can carry out reactions that are difficult to achieve with other reagents. Now, the controlled lithiation of a ‘Pacman’ complex is shown to activate the uranium oxo group towards functionalization and single electron transfer.

The accessibility of catalytically active sites in enzymes is maintained by the surrounding amino acid residues, but in synthetic metal clusters, these sites are typically blocked by the organic groups used to coat them. It has now been shown that the accessibility of gold clusters bound by calixarenes can be controlled by tuning the relative sizes of the metal cores and the ligands.

Crystallographically studying chemical reactions is difficult because the intermediates are rarely stable enough to be crystallized. Now, protein crystals have been used to trap four reaction intermediates in an aromatic dihydroxylation, showing that an iron peroxo complex is observed.

Using a chemical model, the binding of a monovalent ligand and the clustering of a membrane-embedded receptor are shown to be closely related processes that modulate each other without the contribution of any apparent multivalence effect.

Understanding how biosilica forms is crucial to our knowledge of this important biomaterial. Now, the role of collagen as structuring agent for the metre-long spicules of a primitive glass sponge has been revealed and found to have an unusual peptide motif.

Supramolecular gels show promise in diverse areas, including healthcare and energy technologies, owing to tunable properties that arise directly from the organization of their building blocks. Researchers have now been able to control this behaviour by combining enzymatic catalysis with molecular self-assembly. Although it seems counter-intuitive, gels that assembled faster showed fewer defects.

A small-molecule-affinity tag has been designed to mediate the selective isolation of G-quadruplex nucleic acids in a structure-dependant manner. This concept has been applied to the pull-down of G-quadruplex-containing fragments from human cells, and the methodology holds promise for the elucidation of their putative biological functions.

From humble beginnings in Siberia, ruthenium has blossomed into an incredibly interesting and useful element. Simon Higgins looks at its role in past — and perhaps future — Nobel Prize-winning discoveries.