Volume 9 Issue 7, July 2017

Louis Pasteur was a scientific giant of the nineteenth century, but, as Joseph Gal asks, was his most famous contribution to the understanding of chemistry — chirality — influenced more by his artistic talents?

Michelle Francl reminds us that you don't need to look like Einstein to be a scientist.

Disentangling the chemistry and physics behind reported unconventional superconductivity and exotic magnetism in alkali-intercalated PAHs has remained problematic due to the lack of phase-pure samples. Two synthetic pathways have now remedied this issue, facilitating studies of cooperative electronic properties based on carbon π-electrons.

Two papers provide insight into the reactivity of cytochrome P450s. A direct link between electron donation and reactivity has been shown with a selenocysteine-ligated P450 compound I, whereas a serine-ligated P450 (P411) has been engineered to catalyse an intermolecular C–H amination via nitrene transfer.

Lipid bilayers form the thin and floppy membranes that define the boundary of compartments such as cells. Now, a method to control the shape and size of bilayers using DNA nanoscaffolds has been developed. Such designer materials advance synthetic biology and could find use in membrane research.

The secondary and tertiary structure of a protein has profound implications on function and catalysis. Now, both the secondary and tertiary structures of a synthetic polymer have been utilized to catalyse the polymerization of N-carboxyanhydrides. Both the folding of the resulting polypeptides into α-helices and their macromolecular organization dramatically enhance the polymerization rate.

The oxidative prowess of cytochrome P450s has been suggested to stem from the electron-donating axial ligand. Now, a selenocysteine-ligated P450 compound I has been trapped and characterized providing an avenue to examine this hypothesis. Measurements reveal that the selenolate-ligated compound I cleaves C–H bonds more rapidly than the wild-type equivalent.

The intermolecular amination of C–H bonds is an enabling transformation for the synthesis of nitrogen-containing molecules; however, developing catalysts for this class of reactions is very challenging. Now, an iron-based enzyme for this reaction has been engineered, demonstrating that a protein can confer a difficult new function upon an otherwise unreactive base metal.

Cooperative electronic properties that arise purely from carbon π-electrons can lead to unconventional superconductivity and quantum magnetism. New packing architectures have now been established in two caesium-intercalated polyaromatic hydrocarbons, CsPhenanthrene and Cs₂Phenanthrene, both strongly correlated multi-orbital Mott insulators. The frustrated magnetic topology in CsPhenanthrene also renders it a spin-½ quantum spin liquid candidate.

Reports of superconductivity in K_xPicene spurred interest in alkali-intercalated polyaromatic hydrocarbon (PAH) compounds, but their compositions and structures have remained unclear. Now crystalline K₂Pentacene and K₂Picene — neither of which are superconducting — have been prepared by mild synthesis. Structural analysis shows that the cation sites arise within the molecular layers from reorientation of the PAHs within a herringbone packing.

Controlling liposome shape, arrangement and dynamics is important for biophysical studies and synthetic biology applications. Now, using a family of reconfigurable DNA nanocages as templates, spherical, tubular, toroidal and helical liposomes with predefined geometry have been produced. DNA-guided membrane fusion and bending is also demonstrated.

Photoreceptors play an essential role in determining the fate of subsequent biological reactions, however, tracking their structural evolution on ultrafast timescales has been challenging. Now, photoactive yellow protein has been studied using time-domain Raman spectroscopy with sub-7-femtosecond pulses, revealing the ultrafast rearrangement of its hydrogen-bonding structure and also the structure of the first photocycle intermediate.

A squaramide-based anion transporter has now been shown to cause changes in the lysosomal pH leading to impairment of lysosomal enzyme activity and disruption of autophagic processes. The study provides the first experimental evidence that synthetic ion transporters can both disrupt autophagy and induce apoptosis.

The analysis of complex (bio)molecules by NMR spectroscopy is often complicated by limitations in sensitivity. Now, it has been shown that ¹³C NMR signals are strongly enhanced in solution by resonant microwave irradiation of a nitroxide polarizer. This method exhibits up to one-thousand-fold improvements in sensitivity, which stands to greatly improve the detail with which small molecules and metabolites can be studied.

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.

The properties of discrete species can sometimes be improved by fixing them into extended materials. This strategy has now been applied to silver(I) chalcogenide/chalcogenolate clusters, resulting in a metal–organic framework with enhanced stability and fluorescent sensing capabilities. Crystallographic analysis allows precise structural determination of guest binding, which is responsible for both emission turn-off and multicoloured turn-on.

Radical SAM enzymes are versatile enzymes catalysing chemically challenging reactions. Now, a radical SAM enzyme that post-translationally modifies ribosomally synthesized peptides to contain D-amino acids has been discovered in Bacillus subtilis, and its mechanism has been deciphered. These peptides, called epipeptides, efficiently inhibit bacterial growth.

Electron-transfer-mediated decay (ETMD) is a recently discovered type of electronic relaxation that involves the refilling of a core hole by an electron from a neighbouring species. It has now been observed in LiCl solution, when previously it had only been seen in rare-gas clusters. Spectra generated during ETMD are observed to be sensitive to the immediate environment of the initially ionized ion.

Abiotic hydrogel polymer nanoparticles with affinity for a key vascular endothelial growth factor (VEGF₁₆₅) have now been developed. This high-protein affinity was engineered by carefully controlling the amount and the substitution pattern of sulfated N-acetylglucosamines and the inclusion of a hydrophobic group in the monomer.

Brett F. Thornton and Shawn C. Burdette relate how element 100 was first identified in a nuclear weapons test, but that was classified information, so researchers had to 'discover' it again using other methods.