Nature Chemistry presents a Focus which explores the origins of RNA and its role in contemporary biological systems. The collection of articles reveal new insights into what early Earth might have looked like and how life first emerged.
Sending a message to the other side p403 doi:10.1038/nchem.2776 A range of mechanisms have evolved for communicating information across cell membranes, but designing synthetic analogues is far from trivial. A collection of articles in this issue discuss different methods of passing chemical information across lipid bilayers using artificial systems.
Transmembrane Signalling: Membrane messengers pp406 - 407 Scott L. Cockroft doi:10.1038/nchem.2775 Life has evolved elaborate means of communicating essential chemical information across cell membranes. Inspired by biology, two new artificial mechanisms have now been developed that use synthetic messenger molecules to relay chemical signals into or across lipid membranes.
Cation-π Interactions: Mimicking mussel mechanics pp408 - 409 Henrik Birkedal doi:10.1038/nchem.2774 Gluing materials together underwater is a mighty challenge faced — and overcome — by mussels. It requires good adhesion and cohesion. Molecular-level mechanical measurements have now shown that cation-π interactions provide surprisingly strong cohesive abilities.
Helium Chemistry: React with nobility pp409 - 410 Maosheng Miao doi:10.1038/nchem.2768 Helium, the 'most noble' of the noble gases, had only been coaxed into forming molecular ions or van der Waals compounds. It has now been seen in a stable solid compound, Na2He, under high pressure.
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The assembly of transmembrane barrels formed from short synthetic peptides has not been previously demonstrated. Now, a transmembrane pore has been fabricated via the self-assembly of peptides. The 35-amino-acid α-helical peptides are based on the C-terminal D4 domain of the Escherichia coli polysaccharide transporter Wza.
A dynamic foldamer scaffold has now been ligated to a water-compatible, metal-centred binding site and a conformationally responsive fluorophore to form a receptor mimic that inserts into the membrane of artificial vesicles. Binding of specific carboxylate ligands induces a global conformational change that depends on the structure of the ligand, and can be detected via fluorescence. Chemical compounds See also:News and Views by Cockroft
The transmission of chemical information across lipid bilayer membranes is crucial in biological systems. Now, an artificial chemical system able to both transduce and amplify chemical signals across a membrane has been developed. The system works by exploiting the controlled translocation of a synthetic molecule that is embedded within a vesicle membrane. Chemical compounds See also:News and Views by Cockroft
Genetic circuits are important for synthetic biology, biochemistry and bioengineering. Now, the encapsulation of genetic circuits into liposomes has been shown to enable a more modular design, the selective isolation of reactions from the environment and from each other, and the hierarchical assembly of reaction products.
Helium is generally recognized as being chemically inert. A thermodynamically stable compound of helium and sodium, Na2He, has been predicted computationally and then synthesized at high pressure. It exists as an electride, where strongly localized electrons serve as anions located at the centre of Na8 cubes.
Parallel kinetic resolution (PKR) of N-heterocycles via asymmetric acylation has been achieved using quasienantiomers of polymer supported hydroxamic acid reagents. Flow techniques provide physical separation of the reagents, establishing a practical implementation of PKR. The enantioenriched amide products can be readily deprotected to reveal the desired amine without detectable epimerization. Chemical compounds
Although the synthetic chemistry of carbon dioxide has generally been limited to two-electron pathways, single-electron mechanisms would open avenues to new reactivity. Now, the coupling of carbon dioxide and amines to produce α-amino acids can be achieved by an organic photoredox catalyst in continuous flow. Chemical compounds
Understanding how oxygen-evolution reaction (OER) catalysts work is important for the development of efficient energy storage technologies. It has now been shown that lattice oxygen participates in O2 generation during the OER on some highly active metal oxides and that this behaviour becomes more prevalent with greater metal–oxygen covalency.
Using self-assembly to generate hydrogen-bonded organic networks is an underexplored method when preparing functional framework materials. Now, taking cue from DNA, bio-inspired G-quadruplexes are used as both intrinsic electron donors and hydrogen-bonding linkers to assemble rylene diimide acceptors. The resulting rectangular grids form layered crystalline frameworks, in which photoexcitation produces long-lived mobile charge carriers.
Cation–π interactions are critical for the adhesion proteins of marine organisms, yet the energetics of cation–π interactions in underwater environments remains uncharted. Nanoscale force measurements and NMR spectroscopy reveal that interfacial confinement fundamentally alters the energetics of cation–π mediated assembly.
Effective regulation over the motion of self-propelled micro- and nanomotors is a challenging proposition. Now, self-assembled stomatocyte nanomotors with thermoresponsive polymer brushes have been designed that sense changes in local temperature and regulate the accessibility of the hydrogen peroxide fuel — thereby adjusting the speed and behaviour of nanomotor itself.
Higher-order cycloadditions — cycloadditions involving more than six π electrons — provide easy access to complex molecules containing heterocyclic or carbocyclic scaffolds. Now, it has been shown that aminocatalytic activation of 2-cycloalkenones affords mixtures of dienamines that can undergo [6 + 4] cycloadditions with heptafulvenes through a cross dienamine, or [8 + 2] cycloadditions through a linear dienamine. Chemical compounds
Unlike in biomolecular systems, synthetic self-assembly is largely spontaneous, thus limiting the complexity and functionality of the materials one can create. Now, self-assembly under out-of-equilibrium conditions is demonstrated for a metastable supramolecular system. Differentiation of nanoparticles into nanofibres and nanosheets — with electronically distinct states — is achieved through kinetic control, illustrating pathway-dependent material properties. Chemical compounds
Tin can p500 Michael A. Tarselli doi:10.1038/nchem.2769 Tin has been ubiquitous throughout the course of human history, from Bronze Age tools to lithium-ion battery components, yet Michael A. Tarselli warns it should not be deemed pedestrian. Its tendency to linger in human tissues presents a dangerous side that steers researchers towards greener chemistries.
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