Articles in 2017

An attractive feature of supramolecular polymers is their reversibility — they typically depolymerize upon heating. Now, in the presence of a scavenger molecule, a metalloporphyrin derivative bearing eight amide-containing side chains has been shown to undergo supramolecular polymerization on heating as well as cooling through π-stacking and multivalent hydrogen-bonding interactions.

Ultrafast-scanning fluorescence correlation spectroscopy has now been used to measure the molecular interactions underlying the phase behaviour of disordered proteins. Sequence-encoded conformational fluctuations of these proteins are shown to give rise to phase-separated droplets of surprisingly low concentrations. These results provide insight into how the structural features of the droplets affect the properties of liquid-phase intracellular organelles.

The direct, selective conversion of linear alkanes to α-olefins — without isomerization — is an important reaction in the field of catalysis from both a fundamental and industrial perspective. Now, a detailed pathway has been described for how a base metal can promote such a reaction with several turnovers, in a non-oxidative set of C–H activation reactions, thus preventing olefin isomerization.

The catalytic asymmetric α-alkylation of aldehydes has historically been a significant challenge within organic synthesis. Now, this elusive transformation has been achieved through the merger of organocatalysis, photoredox catalysis and hydrogen-atom transfer catalysis to enable the coupling of simple olefins and aldehydes.

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.

Both click chemistry and polymer synthesis require reliable transformations with high selectivity, efficiency and fidelity. Now, bifluoride salts can be used as powerful catalysts for the sufur(VI) fluoride exchange (SuFEx) click reaction and they are applied to the synthesis of polysulfates and polysulfonates in a practical and scalable manner.

Previous methods to transform unsaturated substrates into carbonyl-containing products have generally relied on the use of hazardous carbon monoxide and tailor-made catalysts for each nucleophile employed. Now, shuttle catalysis can be used to perform a CO- and HCl-free transfer hydrochlorocarbonylation to access acid chlorides that can be transformed in situ into virtually any carbonyl-containing product.

The total synthesis of tubingensin B — an indole diterpenoid that bears a daunting chemical structure — has now been achieved. The design and evolution of this succinct total synthesis underscores the utility of long-avoided aryne intermediates for the introduction of structural motifs that have conventionally been viewed as challenging.

With recent and improved understanding of how nuclear and electronic degrees of freedom can interact with each other comes the opportunity to directly control electronic processes. Now it has been shown that ultrafast vibrational excitation can direct light-induced intramolecular electron transfer along a specific path.

It is still a great challenge to synthesize value-added products with two or more carbons directly from CO₂. Now, a bifunctional catalyst composed of reducible metal oxides (In₂O₃) and zeolites (HZSM-5) is prepared and yields high selectivity to gasoline-range hydrocarbons (78.6%) with a high octane number directly from CO₂ hydrogenation.

X-ray and neutron diffraction studies, in conjunction with quantum chemical techniques, have been used to define a new oxidative bond activation pathway that involves simultaneous activation of both bonds of a β-diketiminate-stabilized GaH₂ unit at a single metal centre.

Uncovering the microscopic details of protein–protein association via direct molecular dynamics (MD) simulations has been prevented by the excessive lifetimes of associated states. Now, association and dissociation for the barnase–barstar complex has been studied by adaptive high-throughput MD simulations and Markov modelling, revealing intermediate structures, energetics and kinetics on microseconds-to-hours timescales.

The asymmetric Doyle–Kirmse reaction using chiral Rh(II)- or Cu(I)-catalysts provides SCF₃-containing compounds in a highly efficient and enantioselective manner. The reaction proceeds through enantioselective formation of sulfonium ylide from a diazoester and allyl- or propargyl trifluoromethyl sulfide, followed by concerted [2,3]-sigmatropic rearrangement with the transfer of chirality from sulfur to carbon.

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.

An enzyme (AspRedAm) capable of coupling carbonyls with a variety of amines in a reductive amination has now been discovered. Kinetic studies revealed that the enzyme catalysed both the imine formation step, as well as the reduction step. Structure and mutagenesis studies have highlighted essential catalytic residues and preparative scale examples have demonstrated total turnover numbers of up to 32,000.

Singlet fission — converting a singlet exciton to two triplet excitons — may be useful for improving photovoltaic efficiency. Ultrafast spectroscopic measurements and quantum chemical calculations have now uncovered aspects of the process critical to it occurring efficiently, including the role of intermolecular vibrations and symmetry breaking, and the location of a conical intersection on the excited-state potential-energy surface.

The trapping of antibodies in endosomes often limits their use for intracellular targeting. Now, a single amino acid substitution on a spider-venom peptide has been shown to attenuate the cell membrane lytic activity and enables the selective rupturing of endosomal membranes. The peptide can be used to facilitate the escape of antibodies from endosomes into the cytosol.

Cancer stem cells are typically refractory to conventional treatments. Now, an unprecedented mechanism has been discovered by which salinomycin and derivatives can sequester iron in lysosomes leading to cytoplasmic iron depletion and the subsequent production of reactive oxygen species that are lethal to the cell. This discovery of the importance of iron in cancer stem cell maintenance provides an opportunity for developing new therapeutics.

Unlike in the d block, intervalence charge transfer is rare in the 5f block owing to localized valence electrons and poor overlap between metal and ligand orbitals. Delocalization of 5f electrons has now been observed in a Pu(III)/Pu(IV)–pyridinedicarboxylate solid-state compound. It occurs through metal-to-ligand charge transfer with both plutonium centres.