Targeting tennessine Nat. Chem. (IF 26.201) Pub Date : 2018-10-19 Elizabeth Williams
Targeting tennessineTargeting tennessine, Published online: 19 October 2018; doi:10.1038/s41557-018-0160-2Liz Williams explores the synthesis of tennessine, a story in which elements in supporting roles play a crucial part.
Crumple zones in MOFs Nat. Chem. (IF 26.201) Pub Date : 2018-10-19 Jürgen Senker
Crumple zones in MOFsCrumple zones in MOFs, Published online: 19 October 2018; doi:10.1038/s41557-018-0161-1The applicability of metal-organic frameworks (MOFs) — in spite of their obvious potential — is hindered by stability issues, in particular towards water. Now, a ‘crumple zone’ concept has been proposed in which the presence of sacrificial bonds protects a MOF without significantly altering its structure or functionality.
A crystalline monosubstituted carbene Nat. Chem. (IF 26.201) Pub Date : 2018-10-15 Ryo Nakano, Rodolphe Jazzar, Guy Bertrand
By flanking a carbene carbon with two substituents, it is possible to synthesize persistent triplet carbenes and isolable singlet carbenes. Isolable singlet carbenes are among the most powerful tools in chemistry, and they have even found medicinal and materials science applications. Between the rich chemistry of disubstituted carbenes and the transient parent carbene are the monosubstituted carbenes that, so far, have only been observed in matrices at very low temperatures of just a few K. Herein, we describe the synthesis of a crystalline monosubstituted carbene. The key for isolating such a species was to design the correct substituent, namely a benzo[c]pyrrolidino heterocycle, which can single-handedly tame the intrinsic tendency of carbenes towards dimerization. The π-donor ability of the nitrogen atom, coupled with the steric bulk of chemically inert substituents at the two adjacent quaternary carbons, make these scaffolds very attractive for the isolation of a variety of other hitherto elusive electron-deficient species.
Mining the cellular inventory of pyridoxal phosphate-dependent enzymes with functionalized cofactor mimics Nat. Chem. (IF 26.201) Pub Date : 2018-10-08 Annabelle Hoegl, Matthew B. Nodwell, Volker C. Kirsch, Nina C. Bach, Martin Pfanzelt, Matthias Stahl, Sabine Schneider, Stephan A. Sieber
Pyridoxal phosphate (PLP) is an enzyme cofactor required for the chemical transformation of biological amines in many central cellular processes. PLP-dependent enzymes (PLP-DEs) are ubiquitous and evolutionarily diverse, making their classification based on sequence homology challenging. Here we present a chemical proteomic method for reporting on PLP-DEs using functionalized cofactor probes. We synthesized pyridoxal analogues modified at the 2′-position, which are taken up by cells and metabolized in situ. These pyridoxal analogues are phosphorylated to functional cofactor surrogates by cellular pyridoxal kinases and bind to PLP-DEs via an aldimine bond which can be rendered irreversible by NaBH4 reduction. Conjugation to a reporter tag enables the subsequent identification of PLP-DEs using quantitative, label-free mass spectrometry. Using these probes we accessed a significant portion of the Staphylococcus aureus PLP-DE proteome (73%) and annotate uncharacterized proteins as novel PLP-DEs. We also show that this approach can be used to study structural tolerance within PLP-DE active sites and to screen for off-targets of the PLP-DE inhibitor d-cycloserine.
Catalytic dehydrogenative decarboxyolefination of carboxylic acids Nat. Chem. (IF 26.201) Pub Date : 2018-10-08 Xiang Sun, Junting Chen, Tobias Ritter
Alkenes are among the most versatile building blocks and are widely used for the production of polymers, detergents and synthetic lubricants. Currently, alkenes are sourced from petroleum feedstocks such as naphtha. In light of the necessity to invent sustainable production methods, multiple approaches to making alkenes from abundant fatty acids have been evaluated. However, all attempts so far have required at least one stoichiometric additive, which is an obstruction for applications at larger scales. Here, we report an approach to making olefins from carboxylic acids, in which every additional reaction constituent can be used as a catalyst. We show how abundant fatty acids can be converted to alpha-olefins, and expand the method to include structurally complex carboxylic acids, giving access to synthetically versatile intermediates. Our approach is enabled by the cooperative interplay between a cobalt catalyst, which functions as a proton reduction catalyst, and a photoredox catalyst, which mediates oxidative decarboxylation; coupling both processes enables catalytic conversion of carboxylic acids to olefins.
Inhibiting amyloid-ß cytotoxicity through its interaction with the cell surface receptor LilrB2 by structure-based design Nat. Chem. (IF 26.201) Pub Date : 2018-10-08 Qin Cao, Woo Shik Shin, Henry Chan, Celine K. Vuong, Bethany Dubois, Binsen Li, Kevin A. Murray, Michael R. Sawaya, Juli Feigon, Douglas L. Black, David S. Eisenberg, Lin Jiang
Inhibiting the interaction between amyloid-ß (Aß) and a neuronal cell surface receptor, LilrB2, has been suggested as a potential route for treating Alzheimer’s disease. Supporting this approach, Alzheimer’s-like symptoms are reduced in mouse models following genetic depletion of the LilrB2 homologue. In its pathogenic, oligomeric state, Aß binds to LilrB2, triggering a pathway to synaptic loss. Here we identify the LilrB2 binding moieties of Aß (16KLVFFA21) and identify its binding site on LilrB2 from a crystal structure of LilrB2 immunoglobulin domains D1D2 complexed to small molecules that mimic phenylalanine residues. In this structure, we observed two pockets that can accommodate the phenylalanine side chains of KLVFFA. These pockets were confirmed to be 16KLVFFA21 binding sites by mutagenesis. Rosetta docking revealed a plausible geometry for the Aß–LilrB2 complex and assisted with the structure-guided selection of small molecule inhibitors. These molecules inhibit Aß–LilrB2 interactions in vitro and on the cell surface and reduce Aß cytotoxicity, which suggests these inhibitors are potential therapeutic leads against Alzheimer’s disease.
Quantum-state-controlled channel branching in cold Ne(3P2)+Ar chemi-ionization Nat. Chem. (IF 26.201) Pub Date : 2018-10-08 Sean D. S. Gordon, Juan J. Omiste, Junwen Zou, Silvia Tanteri, Paul Brumer, Andreas Osterwalder
A prerequisite to gain a complete understanding of the most basic aspects of chemical reactions is the ability to perform experiments with complete control over the reactant degrees of freedom. By controlling these, details of a reaction mechanism can be investigated and ultimately manipulated. Here, we present a study of chemi-ionization—a fundamental energy-transfer reaction—under completely controlled conditions. The collision energy of the reagents was tuned from 0.02 K to 1,000 K, with the orientation of the excited Ne atom relative to Ar fully specified by an external magnetic field. Chemi-ionization of Ne(3P2) and Ar in these conditions enables a detailed investigation of how the reaction proceeds, and provides us with a means to control the branching ratio between the two possible reaction outcomes. The merged-beam experimental technique used here allows access to a low-energy regime in which the atoms dynamically reorient into a favourable configuration for reaction, irrespective of their initial orientations.
Cavitation energies can outperform dispersion interactions Nat. Chem. (IF 26.201) Pub Date : 2018-10-08 Suhang He, Frank Biedermann, Nina Vankova, Lyuben Zhechkov, Thomas Heine, Roy E. Hoffman, Alfonso De Simone, Timothy T. Duignan, Werner M. Nau
The accurate dissection of binding energies into their microscopic components is challenging, especially in solution. Here we study the binding of noble gases (He–Xe) with the macrocyclic receptor cucurbituril in water by displacement of methane and ethane as 1H NMR probes. We dissect the hydration free energies of the noble gases into an attractive dispersive component and a repulsive one for formation of a cavity in water. This allows us to identify the contributions to host–guest binding and to conclude that the binding process is driven by differential cavitation energies rather than dispersion interactions. The free energy required to create a cavity to accept the noble gas inside the cucurbituril is much lower than that to create a similarly sized cavity in bulk water. The recovery of the latter cavitation energy drives the overall process, which has implications for the refinement of gas-storage materials and the understanding of biological receptors.
Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water Nat. Chem. (IF 26.201) Pub Date : 2018-10-01 Xiaoyan Wang, Linjiang Chen, Samantha Y. Chong, Marc A. Little, Yongzhen Wu, Wei-Hong Zhu, Rob Clowes, Yong Yan, Martijn A. Zwijnenburg, Reiner Sebastian Sprick, Andrew I. Cooper
Nature uses organic molecules for light harvesting and photosynthesis, but most man-made water splitting catalysts are inorganic semiconductors. Organic photocatalysts, while attractive because of their synthetic tunability, tend to have low quantum efficiencies for water splitting. Here we present a crystalline covalent organic framework (COF) based on a benzo-bis(benzothiophene sulfone) moiety that shows a much higher activity for photochemical hydrogen evolution than its amorphous or semicrystalline counterparts. The COF is stable under long-term visible irradiation and shows steady photochemical hydrogen evolution with a sacrificial electron donor for at least 50 hours. We attribute the high quantum efficiency of fused-sulfone-COF to its crystallinity, its strong visible light absorption, and its wettable, hydrophilic 3.2 nm mesopores. These pores allow the framework to be dye-sensitized, leading to a further 61% enhancement in the hydrogen evolution rate up to 16.3 mmol g−1 h−1. The COF also retained its photocatalytic activity when cast as a thin film onto a support.
Superoxide dismutase activity enabled by a redox-active ligand rather than metal Nat. Chem. (IF 26.201) Pub Date : 2018-10-01 Meghan B. Ward, Andreas Scheitler, Meng Yu, Laura Senft, Annika S. Zillmann, John D. Gorden, Dean D. Schwartz, Ivana Ivanović-Burmazović, Christian R. Goldsmith
Reactive oxygen species are integral to many physiological processes. Although their roles are still being elucidated, they seem to be linked to a variety of disorders and may represent promising drug targets. Mimics of superoxide dismutases, which catalyse the decomposition of O2•− to H2O2 and O2, have traditionally used redox-active metals, which are toxic outside of a tightly coordinating ligand. Purely organic antioxidants have also been investigated but generally require stoichiometric, rather than catalytic, doses. Here, we show that a complex of the redox-inactive metal zinc(ii) with a hexadentate ligand containing a redox-active quinol can catalytically degrade superoxide, as demonstrated by both reactivity assays and stopped-flow kinetics studies of direct reactions with O2•− and the zinc(ii) complex. The observed superoxide dismutase catalysis has an important advantage over previously reported work in that it is hastened, rather than impeded, by the presence of phosphate, the concentration of which is high under physiological conditions.
SNAr stands corrected Nat. Chem. (IF 26.201) Pub Date : 2018-09-20 Yinghua Jin, Wei Zhang
SNAr stands correctedS<sub>N</sub>Ar stands corrected, Published online: 20 September 2018; doi:10.1038/s41557-018-0138-0Dynamic covalent chemistry combines the error-correcting behaviour of supramolecular chemistry with the robustness of covalent bonding, but relies on a somewhat limited set of reactions. Now, the classic nucleophilic aromatic substitution (SNAr) reaction has been shown to be reversible and self-correcting.
Hafnium the lutécium I used to be Nat. Chem. (IF 26.201) Pub Date : 2018-09-20 Shawn C. Burdette, Brett F. Thornton
Hafnium the lutécium I used to beHafnium the lutécium I used to be, Published online: 20 September 2018; doi:10.1038/s41557-018-0140-6Shawn C. Burdette and Brett F. Thornton examine hafnium’s emergence from ores containing a seemingly identical element to become both a chemical oddity and an essential material for producing nuclear energy.
Catalysis at the limit Nat. Chem. (IF 26.201) Pub Date : 2018-09-20 Christian Papp
Catalysis at the limitCatalysis at the limit, Published online: 20 September 2018; doi:10.1038/s41557-018-0143-3Probing single-atom alloys has shown that, when interactions between the components are weak, the electronic structure of the dilute element resembles that of a free atom, making bonding with reactants more like that in molecular homogeneous catalysts.
A positive positive to negative Nat. Chem. (IF 26.201) Pub Date : 2018-09-20 Jed F. Fisher, Shahriar Mobashery
A positive positive to negativeA positive positive to negative, Published online: 20 September 2018; doi:10.1038/s41557-018-0148-yThe structure of an antibiotic that is effective against Gram-positive bacteria, but not against Gram-negative bacteria, has now been modified to improve its effectiveness against Gram-negative bacteria. The approach could help broaden the spectrum of activity of other antibiotics.
Carbohydrate stabilization extends the kinetic limits of chemical polysaccharide depolymerization Nat. Chem. (IF 26.201) Pub Date : 2018-09-17 Ydna M. Questell-Santiago, Raquel Zambrano-Varela, Masoud Talebi Amiri, Jeremy S. Luterbacher
Polysaccharide depolymerization is an essential step for valorizing lignocellulosic biomass. In inexpensive systems such as pure water or dilute acid mixtures, carbohydrate monomer degradation rates exceed hemicellulose—and especially cellulose—depolymerization rates at most easily accessible temperatures, limiting sugar yields. Here, we use a reversible stabilization of xylose and glucose by acetal formation with formaldehyde to alter this kinetic paradigm, preventing sugar dehydration to furans and their subsequent degradation. During a harsh organosolv pretreatment in the presence of formaldehyde, over 90% of xylan in beech wood was recovered as diformylxylose (compared to 16% xylose recovery without formaldehyde). The subsequent depolymerization of cellulose led to carbohydrate yields over 70% and a final concentration of ~5 wt%, whereas the same conditions without formaldehyde gave a yield of 28%. This stabilization strategy pushes back the longstanding kinetic limits of polysaccharide depolymerization and enables the recovery of biomass-derived carbohydrates in high yields and concentrations.
Thiophene and its sulfur inhibit indenoindenodibenzothiophene diradicals from low-energy lying thermal triplets Nat. Chem. (IF 26.201) Pub Date : 2018-09-17 Justin J. Dressler, Mitsuru Teraoka, Guzmán L. Espejo, Ryohei Kishi, Shota Takamuku, Carlos J. Gómez-García, Lev N. Zakharov, Masayoshi Nakano, Juan Casado, Michael M. Haley
Many qualitative structure–property correlations between diradical character and emerging molecular properties are known. For example, the increase of diradical character further decreases the singlet–triplet energy gap. Here we show that inclusion of thiophenes within a quinoidal polycyclic hydrocarbon imparts appreciable diradical character yet retains the large singlet–triplet energy gap, a phenomenon that has no precedent in the literature. The low aromatic character of thiophene and its electron-rich nature are the key properties leading to these unique findings. A new indenoindenodibenzothiophene scaffold has been prepared and fully characterized by several spectroscopies, magnetic measurements, solid-state X-ray and state-of-the-art quantum chemical calculations, all corroborating this unique dichotomy between the diradical input and the emerging magnetic properties. New structure–property relationships such as these are not only extremely important in the field of diradical chemistry and organic electronics, but also provide new insights into the versatility of π-electron chemical bonding.
Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions Nat. Chem. (IF 26.201) Pub Date : 2018-09-17 János Pető, Tamás Ollár, Péter Vancsó, Zakhar I. Popov, Gábor Zsolt Magda, Gergely Dobrik, Chanyong Hwang, Pavel B. Sorokin, Levente Tapasztó
The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption however, here we report single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoS2−xOx crystals. Oxygen substitution sites present all over the basal plane act as single-atom reaction centres, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.
Easy as one, two, three Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 Laura Castoldi, Vittorio Pace
Easy as one, two, threeEasy as one, two, three, Published online: 10 September 2018; doi:10.1038/s41557-018-0139-zThe preparation of three-dimensional frameworks with multiple stereocentres from simple acyclic hydrocarbons represents a challenging transformation. Now, starting from simple and readily available reagents, formation of these complex targets can be achieved in just three catalytic transformations with high levels of stereocontrol.
Chromopynones are pseudo natural product glucose uptake inhibitors targeting glucose transporters GLUT-1 and -3 Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 George Karageorgis, Elena S. Reckzeh, Javier Ceballos, Melanie Schwalfenberg, Sonja Sievers, Claude Ostermann, Axel Pahl, Slava Ziegler, Herbert Waldmann
The principles guiding the design and synthesis of bioactive compounds based on natural product (NP) structure, such as biology-oriented synthesis (BIOS), are limited by their partial coverage of the NP-like chemical space of existing NPs and retainment of bioactivity in the corresponding compound collections. Here we propose and validate a concept to overcome these limitations by de novo combination of NP-derived fragments to structurally unprecedented ‘pseudo natural products’. Pseudo NPs inherit characteristic elements of NP structure yet enable the efficient exploration of areas of chemical space not covered by NP-derived chemotypes, and may possess novel bioactivities. We provide a proof of principle by designing, synthesizing and investigating the biological properties of chromopynone pseudo NPs that combine biosynthetically unrelated chromane- and tetrahydropyrimidinone NP fragments. We show that chromopynones define a glucose uptake inhibitor chemotype that selectively targets glucose transporters GLUT-1 and -3, inhibits cancer cell growth and promises to inspire new drug discovery programmes aimed at tumour metabolism.
Author Correction: Amine hemilability enables boron to mechanistically resemble either hydride or proton Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 C. Frank Lee, Diego B. Diaz, Aleksandra Holownia, Sherif J. Kaldas, Sean K. Liew, Graham E. Garrett, Travis Dudding, Andrei K. Yudin
Author Correction: Amine hemilability enables boron to mechanistically resemble either hydride or protonAuthor Correction: Amine hemilability enables boron to mechanistically resemble either hydride or proton, Published online: 10 September 2018; doi:10.1038/s41557-018-0151-3Author Correction: Amine hemilability enables boron to mechanistically resemble either hydride or proton
Gas-phase sugar formation using hydroxymethylene as the reactive formaldehyde isomer Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 André K. Eckhardt, Michael M. Linden, Raffael C. Wende, Bastian Bernhardt, Peter R. Schreiner
Carbohydrates (CH2O)n are the formal adducts of carbon (atoms) to water with a repeating unit that structurally resembles H–C̈–OH (hydroxymethylene). Although hydroxymethylene has been suggested as a building block for sugar formation, it is a reactive species that had escaped detection until recently. Here we demonstrate that formaldehyde reacts with its isomer hydroxymethylene to give glycolaldehyde in a nearly barrierless reaction. This carbonyl–ene-type transformation operates in the absence of base and solvent at cryogenic temperatures similar to those found in extraterrestrial environments or interstellar clouds. Hydroxymethylene acts as a building block for an iterative sugar synthesis, as we demonstrate through the formation of the triose glyceraldehyde. The thermodynamically preferred ketose dihydroxyacetone does not form, and the formation of further branched sugars in the iterative synthesis presented here is unlikely. The results therefore provide a link between the well-known formose (Butlerow) reaction and sugar formation under non-aqueous conditions.
What tangled webs we weave Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 Edward E. Fenlon
What tangled webs we weaveWhat tangled webs we weave, Published online: 10 September 2018; doi:10.1038/s41557-018-0135-3Knots have been rigorously studied since the 1860s, but only in the past 30 years have they been made in the laboratory in molecular form. Now, the most complex small-molecule examples so far — a composite knot and an isomeric link, each with nine crossings — have been prepared.
Formation of the layered conductive magnet CrCl2(pyrazine)2 through redox-active coordination chemistry Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 Kasper S. Pedersen, Panagiota Perlepe, Michael L. Aubrey, Daniel N. Woodruff, Sebastian E. Reyes-Lillo, Anders Reinholdt, Laura Voigt, Zheshen Li, Kasper Borup, Mathieu Rouzières, Dumitru Samohvalov, Fabrice Wilhelm, Andrei Rogalev, Jeffrey B. Neaton, Jeffrey R. Long, Rodolphe Clérac
The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. Here, we report the synthesis of CrCl2(pyrazine)2, an air-stable layered solid, by reaction of CrCl2 with pyrazine (pyz). This compound displays a ferrimagnetic order below ∼55 K, reflecting the presence of strong magnetic interactions. Electrical conductivity measurements demonstrate that CrCl2(pyz)2 reaches a conductivity of 32 mS cm–1 at room temperature, which operates through a 2D hopping-based transport mechanism. These properties are induced by the redox-activity of the pyrazine ligand, which leads to a smearing of the Cr 3d and pyrazine π states. We suggest that the combination of redox-active ligands and reducing paramagnetic metal ions represents a general approach towards tuneable 2D materials that consist of charge-neutral layers and exhibit both long-range magnetic order and high electronic conductivity.
Stereoselective synthesis of a composite knot with nine crossings Nat. Chem. (IF 26.201) Pub Date : 2018-09-10 Liang Zhang, Alexander J. Stephens, Alina L. Nussbaumer, Jean-François Lemonnier, Pia Jurček, Iñigo J. Vitorica-Yrezabal, David A. Leigh
The simultaneous synthesis of a molecular nine-crossing composite knot that contains three trefoil tangles of the same handedness and a 937973 link (a type of cyclic catenane topologically constrained to always have at least three twists within the links) is reported. Both compounds contain high degrees of topological writhe (w = 9), a structural feature of supercoiled DNA. The entwined products are generated from the cyclization of a hexameric Fe(ii) circular helicate by ring-closing olefin metathesis, with the mixture of topological isomers formed as a result of different ligand connectivity patterns. The metal-coordinated composite knot was isolated by crystallization, the topology unambiguously proven by tandem mass spectrometry, with X-ray crystallography confirming that the 324-atom loop crosses itself nine times with matching handedness (all Δ or all Λ) at every metal centre within each molecule. Controlling the connectivity of the ligand end groups on circular metal helicate scaffolds provides an effective synthetic strategy for the stereoselective synthesis of composite knots and other complex molecular topologies.
Dynamic self-correcting nucleophilic aromatic substitution Nat. Chem. (IF 26.201) Pub Date : 2018-09-03 Wen Jie Ong, Timothy M. Swager
Dynamic covalent chemistry, with its ability to correct synthetic dead-ends, allows for the synthesis of elaborate extended network materials in high yields. However, the limited number of reactions amenable to dynamic covalent chemistry necessarily confines the scope and functionality of materials synthesized. Here, we explore the dynamic and self-correcting nature of nucleophilic aromatic substitution (SNAr), using ortho-aryldithiols and ortho-aryldifluorides that condense to produce redox-active thianthrene units. We demonstrate the facile construction of two-, three- and four-point junctions by reaction between a dithiol nucleophile and three different model electrophiles that produces molecules with two, three and four thianthrene moieties, respectively, in excellent yields. The regioselectivity observed is driven by thermodynamics; other connections form under kinetic control. We also show that the same chemistry can be extended to the synthesis of novel ladder macrocycles and porous polymer networks with Brunauer–Emmett–Teller surface area of up to 813 m2 g−1.
Narrow-band single-photon emission through selective aryl functionalization of zigzag carbon nanotubes Nat. Chem. (IF 26.201) Pub Date : 2018-09-03 Avishek Saha, Brendan J. Gifford, Xiaowei He, Geyou Ao, Ming Zheng, Hiromichi Kataura, Han Htoon, Svetlana Kilina, Sergei Tretiak, Stephen K. Doorn
The introduction of sp3 defects into single-walled carbon nanotubes through covalent functionalization can generate new light-emitting states and thus dramatically expand their optical functionality. This may open up routes to enhanced imaging, photon upconversion, and room-temperature single-photon emission at telecom wavelengths. However, a significant challenge in harnessing this potential is that the nominally simple reaction chemistry of nanotube functionalization introduces a broad diversity of emitting states. Precisely defining a narrow band of emission energies necessitates constraining these states, which requires extreme selectivity in molecular binding configuration on the nanotube surface. We show here that such selectivity can be obtained through aryl functionalization of so-called ‘zigzag’ nanotube structures to achieve a threefold narrowing in emission bandwidth. Accompanying density functional theory modelling reveals that, because of the associated structural symmetry, the defect states become degenerate, thus limiting emission energies to a single narrow band. We show that this behaviour can only result from a predominant selectivity for ortho binding configurations of the aryl groups on the nanotube lattice.
Free-atom-like d states in single-atom alloy catalysts Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 M. T. Greiner, T. E. Jones, S. Beeg, L. Zwiener, M. Scherzer, F. Girgsdies, S. Piccinin, M. Armbrüster, A. Knop-Gericke, R. Schlögl
Alloying provides a means by which to tune a metal catalyst’s electronic structure and thus tailor its performance; however, mean-field behaviour in metals imposes limits. To access unprecedented catalytic behaviour, materials must exhibit emergent properties that are not simply interpolations of the constituent components’ properties. Here we show an emergent electronic structure in single-atom alloys, whereby weak wavefunction mixing between minority and majority elements results in a free-atom-like electronic structure on the minority element. This unusual electronic structure alters the minority element’s adsorption properties such that the bonding with adsorbates resembles the bonding in molecular metal complexes. We demonstrate this phenomenon with AgCu alloys, dilute in Cu, where the Cu d states are nearly unperturbed from their free-atom state. In situ electron spectroscopy demonstrates that this unusual electronic structure persists in reaction conditions and exhibits a 0.1 eV smaller activation barrier than bulk Cu in methanol reforming. Theory predicts that several other dilute alloys exhibit this phenomenon, which offers a design approach that may lead to alloys with unprecedented catalytic properties.
Isoreticular two-dimensional magnetic coordination polymers prepared through pre-synthetic ligand functionalization Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 J. López-Cabrelles, S. Mañas-Valero, I. J. Vitórica-Yrezábal, P. J. Bereciartua, J. A. Rodríguez-Velamazán, J. C. Waerenborgh, B. J. C. Vieira, D. Davidovikj, P. G. Steeneken, H. S. J. van der Zant, G. Mínguez Espallargas, E. Coronado
Chemical functionalization is a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, increase their processability and stability, tune their functionalities and, even, create new 2D materials. This is typically achieved through post-synthetic functionalization by anchoring molecules on the surface of an exfoliated 2D crystal, but it inevitably alters the long-range structural order of the material. Here we present a pre-synthetic approach that allows the isolation of crystalline, robust and magnetic functionalized monolayers of coordination polymers. A series of five isostructural layered magnetic coordination polymers based on Fe(ii) centres and different benzimidazole derivatives (bearing a Cl, H, CH3, Br or NH2 side group) were first prepared. On mechanical exfoliation, 2D materials are obtained that retain their long-range structural order and exhibit good mechanical and magnetic properties. This combination, together with the possibility to functionalize their surface at will, makes them good candidates to explore magnetism in the 2D limit and to fabricate mechanical resonators for selective gas sensing.
Efficient and stereodivergent synthesis of unsaturated acyclic fragments bearing contiguous stereogenic elements Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 Jeffrey Bruffaerts, David Pierrot, Ilan Marek
Synthetic organic strategies that enable the catalytic and rapid assembly of a large array of organic compounds that possess multiple stereocentres in acyclic systems are somewhat rare, especially when it comes to reaching today’s high standards of efficiency and selectivity. In particular, the catalytic preparation of a three-dimensional molecular layout of a simple acyclic hydrocarbon skeleton that possesses several stereocentres from simple and readily available reagents still represents a vastly uncharted domain. Here we report a rapid, modular, stereodivergent and diversity-oriented unified strategy to construct acyclic molecular frameworks that bear up to four contiguous and congested stereogenic elements, with remarkably high levels of stereocontrol and in only three catalytic steps from commercially available alkynes. A regio- and diastereoselective catalytic Heck migratory insertion reaction of alkenylcyclopropyl carbinols that merges selective C–C bond cleavage of a cyclopropane represents the key step.
Non-intuitive rotational reorientation in collisions of NO(A 2Σ+) with Ne from direct measurement of a four-vector correlation Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 Thomas R. Sharples, Joseph G. Leng, Thomas F. M. Luxford, Kenneth. G. McKendrick, Pablo G. Jambrina, F. Javier Aoiz, David W. Chandler, Matthew L. Costen
Stereodynamic descriptions of molecular collisions concern the angular correlations that exist between vector properties of the motion of the participating species, including their velocities and rotational angular momenta. Measurements of vector correlations provide a unique view of the forces acting during collisions, and are a stringent test of electronic-structure calculations of molecular interactions. Here, we present direct measurement of the four-vector correlation between initial and final relative velocities and rotational angular momenta in a molecular collision. This property, which quantifies the extent to which a molecule retains a memory of its initial sense of rotation, or handedness, as a function of scattering angle, yields insight into the dynamics of a molecular collision. We report non-intuitive changes in the handedness for specific states and scattering angles, reproduced by classical and quantum scattering calculations. Comparison to calculations on different ab initio potential energy surfaces demonstrates this measurement’s exquisite sensitivity to the underlying intermolecular forces.
Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 Franck Para, Franck Bocquet, Laurent Nony, Christian Loppacher, Michel Féron, Fréderic Cherioux, David Z. Gao, Filippo Federici Canova, Matthew B. Watkins
On-surface polymerization is a promising technique to prepare organic functional nanomaterials that are challenging to synthesize in solution, but it is typically used on metal substrates, which play a catalytic role. Previous examples on insulating surfaces have involved intermediate self-assembled structures, which face high barriers to diffusion, or annealing to higher temperatures, which generally causes rapid dewetting and desorption of the monomers. Here we report the photoinitiated radical polymerization, initiated from a two-dimensional gas phase, of a dimaleimide monomer on an insulating KCl surface. Polymer fibres up to 1 μm long are formed through chain-like rather than step-like growth. Interactions between potassium cations and the dimaleimide’s oxygen atoms facilitate the propagation of the polymer fibres along a preferred axis of the substrate over long distances. Density functional theory calculations, non-contact atomic force microscopy imaging and manipulations at room temperature were used to explore the initiation and propagation processes, as well as the structure and stability of the resulting one-dimensional polymer fibres.
A fluorescent membrane tension probe Nat. Chem. (IF 26.201) Pub Date : 2018-08-27 Adai Colom, Emmanuel Derivery, Saeideh Soleimanpour, Caterina Tomba, Marta Dal Molin, Naomi Sakai, Marcos González-Gaitán, Stefan Matile, Aurélien Roux
Cells and organelles are delimited by lipid bilayers in which high deformability is essential to many cell processes, including motility, endocytosis and cell division. Membrane tension is therefore a major regulator of the cell processes that remodel membranes, albeit one that is very hard to measure in vivo. Here we show that a planarizable push–pull fluorescent probe called FliptR (fluorescent lipid tension reporter) can monitor changes in membrane tension by changing its fluorescence lifetime as a function of the twist between its fluorescent groups. The fluorescence lifetime depends linearly on membrane tension within cells, enabling an easy quantification of membrane tension by fluorescence lifetime imaging microscopy. We further show, using model membranes, that this linear dependency between lifetime of the probe and membrane tension relies on a membrane-tension-dependent lipid phase separation. We also provide calibration curves that enable accurate measurement of membrane tension using fluorescence lifetime imaging microscopy.
Beyond the typical role of solvent Nat. Chem. (IF 26.201) Pub Date : 2018-08-21 Gilles H. Peslherbe
Beyond the typical role of solvent Beyond the typical role of solvent, Published online: 21 August 2018; doi:10.1038/s41557-018-0130-8 State-of-the-art quantum simulations predict that solvent molecules may partner with a solute in solution to form stable chemically distinct coordination species that interconvert from one to another. The solvent would thus be directly implicated in chemical reactions.
N-doping goes sp-hybridized Nat. Chem. (IF 26.201) Pub Date : 2018-08-21 Yao Zheng, Shi-Zhang Qiao
N-doping goes sp-hybridized N-doping goes sp-hybridized, Published online: 21 August 2018; doi:10.1038/s41557-018-0129-1 Specific forms of nitrogen doping can endow carbon-based metal-free materials with electrocatalytic activity. Now, introducing sp-hybridized nitrogen atoms into some acetylenic sites of ultra-thin graphdiyne — a highly π-conjugated lamellar carbon allotrope — has led to excellent oxygen reduction reaction activity.
Roentgenium generation Nat. Chem. (IF 26.201) Pub Date : 2018-08-21 Taye B. Demissie
Roentgenium generation Roentgenium generation, Published online: 21 August 2018; doi:10.1038/s41557-018-0131-7 Taye Demissie relates unununium’s unusually smooth route to roentgenium, and how predicting its properties relies on relativistic calculations.
Enzyme-powered motility in buoyant organoclay/DNA protocells Nat. Chem. (IF 26.201) Pub Date : 2018-08-20 B. V. V. S. Pavan Kumar, Avinash J. Patil, Stephen Mann
Reconstitution and simulation of cellular motility in microcompartmentalized colloidal objects have important implications for microcapsule-based remote sensing, environmentally induced signalling between artificial cell-like entities and programming spatial migration in synthetic protocell consortia. Here we describe the design and construction of catalase-containing organoclay/DNA semipermeable microcapsules, which in the presence of hydrogen peroxide exhibit enzyme-powered oxygen gas bubble-dependent buoyancy. We determine the optimum conditions for single and/or multiple bubble generation per microcapsule, monitor the protocell velocities and resilience, and use remote magnetic guidance to establish reversible changes in the buoyancy. Co-encapsulation of catalase and glucose oxidase is exploited to establish a spatiotemporal response to antagonistic bubble generation and depletion to produce protocells capable of sustained oscillatory vertical movement. We demonstrate that the motility of the microcapsules can be used for the flotation of macroscopic objects, self-sorting of mixed protocell communities and the delivery of a biocatalyst from an inert to chemically active environment. These results highlight new opportunities to constructing programmable microcompartmentalized colloids with buoyancy-derived motility.
Activation of diverse carbon–heteroatom and carbon–carbon bonds via palladium(ii)-catalysed β-X elimination Nat. Chem. (IF 26.201) Pub Date : 2018-08-20 Van T. Tran, John A. Gurak Jr, Kin S. Yang, Keary M. Engle
Chemists’ ability to synthesize structurally complex, high-value organic molecules from simple starting materials is limited by methods to selectively activate and functionalize strong alkyl C(sp3) covalent bonds. Recent activity has focused on the activation of abundant C–O, C–N and C–C bonds via a mechanistic paradigm of oxidative addition of a low-valent, electron-rich transition metal. This approach typically employs nickel(0), rhodium(i), ruthenium(0) and iron catalysts under conditions finely tuned for specific, electronically activated substrates, sometimes assisted by chelating functional groups or ring strain. By adopting a redox-neutral strategy involving palladium(ii)-catalysed C–H activation followed by β-heteroatom/carbon elimination, we describe here a catalytic method to activate alkyl C(sp3)–oxygen, nitrogen, carbon, fluorine and sulfur bonds with high regioselectivity. Directed hydrofunctionalization of the resultant palladium(ii)-bound alkene leads to formal functional group metathesis. The method is applied to amino acid upgrading with complete regioselectivity and moderate to high retention of enantiomeric excess. Low-strain heterocycles undergo strong-bond activation and substitution, giving ring-opened products.
Light-driven molecular trap enables bidirectional manipulation of dynamic covalent systems Nat. Chem. (IF 26.201) Pub Date : 2018-08-13 Michael Kathan, Fabian Eisenreich, Christoph Jurissek, Andre Dallmann, Johannes Gurke, Stefan Hecht
Bond formation between two molecular entities in a closed system strictly obeys the principle of microscopic reversibility and occurs in favour of the thermodynamically more stable product. Here, we demonstrate how light can bypass this fundamental limitation by driving and controlling the reversible bimolecular reaction between an N-nucleophile and a photoswitchable carbonyl electrophile. Light-driven tautomerization cycles reverse the reactivity of the C=O/C=N-electrophiles (‘umpolung’) to activate substrates and remove products, respectively, solely depending on the illumination wavelength. By applying either red or blue light, selective and nearly quantitative intermolecular bond formation/scission can be achieved, even if the underlying condensation/hydrolysis equilibrium is thermodynamically disfavoured. Exploiting light-driven in situ C=N exchange, our approach can be used to externally regulate a closed dynamic covalent system by actively and reversibly removing specific components, resembling a molecular and bidirectional version of a macroscopic Dean–Stark trap.
Highly reduced and protonated aqueous solutions of [P2W18O62]6− for on-demand hydrogen generation and energy storage Nat. Chem. (IF 26.201) Pub Date : 2018-08-13 Jia-Jia Chen, Mark D. Symes, Leroy Cronin
As our reliance on renewable energy sources grows, so too does our need to store this energy to mitigate against troughs in supply. Energy storage in batteries or by conversion to chemical fuels are the two most flexible and scalable options, but are normally considered mutually exclusive. Energy storage solutions that can act as both batteries and fuel generation devices (depending on the requirements of the user) could therefore revolutionize the uptake and use of renewably generated energy. Here, we present a polyoxoanion, [P2W18O62]6−, that can be reversibly reduced and protonated by 18 electrons/H+ per anion in aqueous solution, and that can act either as a high-performance redox flow battery electrolyte (giving a practical discharged energy density of 225 Wh l−1 with a theoretical energy density of more than 1,000 Wh l−1), or as a mediator in an electrolytic cell for the on-demand generation of hydrogen.
Hydrolytic stability in hemilabile metal–organic frameworks Nat. Chem. (IF 26.201) Pub Date : 2018-08-13 Lauren N. McHugh, Matthew J. McPherson, Laura J. McCormick, Samuel A. Morris, Paul S. Wheatley, Simon J. Teat, David McKay, Daniel M. Dawson, Charlotte E. F. Sansome, Sharon E. Ashbrook, Corinne A. Stone, Martin W. Smith, Russell E. Morris
Highly porous metal–organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of ‘sacrificial’ bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF’s copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.
The energy-transfer-enabled biocompatible disulfide–ene reaction Nat. Chem. (IF 26.201) Pub Date : 2018-08-06 Michael Teders, Christian Henkel, Lea Anhäuser, Felix Strieth-Kalthoff, Adrián Gómez-Suárez, Roman Kleinmans, Axel Kahnt, Andrea Rentmeister, Dirk Guldi, Frank Glorius
Sulfur-containing molecules participate in many essential biological processes. Of utmost importance is the methylthioether moiety, present in the proteinogenic amino acid methionine and installed in tRNA by radical-S-adenosylmethionine methylthiotransferases. Although the thiol–ene reaction for carbon–sulfur bond formation has found widespread applications in materials or medicinal science, a biocompatible chemo- and regioselective hydrothiolation of unactivated alkenes and alkynes remains elusive. Here, we describe the design of a general chemoselective anti-Markovnikov hydroalkyl/aryl thiolation of alkenes and alkynes—also allowing the biologically important hydromethylthiolation—by triplet–triplet energy transfer activation of disulfides. This fast disulfide–ene reaction shows extraordinary functional group tolerance and biocompatibility. Transient absorption spectroscopy was used to study the sensitization process in detail. The hereby gained mechanistic insights were successfully employed for optimization of the catalytic system. This photosensitized transformation should stimulate bioimaging applications and carbon–sulfur bond-forming late-stage functionalization chemistry, especially in the context of metabolic labelling.
Few-layer graphdiyne doped with sp-hybridized nitrogen atoms at acetylenic sites for oxygen reduction electrocatalysis Nat. Chem. (IF 26.201) Pub Date : 2018-08-06 Yasong Zhao, Jiawei Wan, Huiying Yao, Lijuan Zhang, Kaifeng Lin, Lei Wang, Nailiang Yang, Daobin Liu, Li Song, Jia Zhu, Lin Gu, Lei Liu, Huijun Zhao, Yuliang Li, Dan Wang
The oxygen reduction reaction (ORR) is a fundamental reaction for energy storage and conversion. It has mainly relied on platinum-based electrocatalysts, but the chemical doping of carbon-based materials has proven to be a promising strategy for preparing metal-free alternatives. Nitrogen doping in particular provides a diverse range of nitrogen forms. Here, we introduce a new form of nitrogen doping moieties —sp-hybridized nitrogen (sp-N) atoms into chemically defined sites of ultrathin graphdiyne, through pericyclic replacement of the acetylene groups. The as-prepared sp-N-doped graphdiyne catalyst exhibits overall good ORR performance, in particular with regards to peak potential, half-wave potential and current density. Under alkaline conditions it was comparable to commercial Pt/C, and showed more rapid kinetics. And although its performances are a bit lower than those of Pt/C in acidic media they surpass those of other metal-free materials. Taken together, experimental data and density functional theory calculations suggest that the high catalytic activity originates from the sp-N dopant, which facilitates O2 adsorption and electron transfer on the surface of the catalyst. This incorporation of chemically defined sp-N atoms provides a new synthetic route to high-performance carbon-based and other metal-free catalysts.
Design of catalysts for site-selective and enantioselective functionalization of non-activated primary C–H bonds Nat. Chem. (IF 26.201) Pub Date : 2018-08-06 Kuangbiao Liao, Yun-Fang Yang, Yingzi Li, Jacob N. Sanders, K. N. Houk, Djamaladdin G. Musaev, Huw M. L. Davies
C–H functionalization represents a promising approach for the synthesis of complex molecules. Instead of relying on modifying the functional groups present in a molecule, the synthetic sequence is achieved by carrying out selective reactions on the C–H bonds, which traditionally would have been considered to be the unreactive components of a molecule. A major challenge is to design catalysts to control both the site- and stereoselectivity of the C–H functionalization. We have been developing dirhodium catalysts with different selectivity profiles in C–H functionalization reactions with donor/acceptor carbenes as reactive intermediates. Here we describe a new dirhodium catalyst capable of the functionalization of non-activated primary C–H bonds with high levels of site selectivity and enantioselectivity.
Metathesis-active ligands enable a catalytic functional group metathesis between aroyl chlorides and aryl iodides Nat. Chem. (IF 26.201) Pub Date : 2018-08-06 Yong Ho Lee, Bill Morandi
Current methods for functional group interconversion have, for the most part, relied on relatively strong driving forces which often require highly reactive reagents to generate irreversibly a desired product in high yield and selectivity. These approaches generally prevent the use of the same catalytic strategy to perform the reverse reaction. Here we describe a catalytic functional group metathesis approach to interconvert, under CO-free conditions, two synthetically important classes of electrophiles that are often employed in the preparation of pharmaceuticals and agrochemicals—aroyl chlorides (ArCOCl) and aryl iodides (ArI). Our reaction design relies on the implementation of a key reversible ligand C–P bond cleavage event, which enables a non-innocent, metathesis-active phosphine ligand to mediate a rapid aryl group transfer between the two different electrophiles. Beyond enabling a practical and safer approach to the interconversion of ArCOCl and ArI, this type of ligand non-innocence provides a blueprint for the development of a broad range of functional group metathesis reactions employing synthetically relevant aryl electrophiles.
Diels–Alder cycloadditions of strained azacyclic allenes Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 Joyann S. Barber, Michael M. Yamano, Melissa Ramirez, Evan R. Darzi, Rachel R. Knapp, Fang Liu, K. N. Houk, Neil K. Garg
For over a century, the structures and reactivities of strained organic compounds have captivated the chemical community. Whereas triple-bond-containing strained intermediates have been well studied, cyclic allenes have received far less attention. Additionally, studies of cyclic allenes that bear heteroatoms in the ring are scarce. We report an experimental and computational study of azacyclic allenes, which features syntheses of stable allene precursors, the mild generation and Diels–Alder trapping of the desired cyclic allenes, and explanations of the observed regio- and diastereoselectivities. Furthermore, we show that stereochemical information can be transferred from an enantioenriched silyl triflate starting material to a Diels–Alder cycloadduct by way of a stereochemically defined azacyclic allene intermediate. These studies demonstrate that heteroatom-containing cyclic allenes, despite previously being overlooked as valuable synthetic intermediates, may be harnessed for the construction of complex molecular scaffolds bearing multiple stereogenic centres.
Hydrogenation catalyst generates cyclic peptide stereocentres in sequence Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 Diane N. Le, Eric Hansen, Hasan A. Khan, Byoungmoo Kim, Olaf Wiest, Vy M. Dong
Molecular recognition plays a key role in enzyme-substrate specificity, the regulation of genes, and the treatment of diseases. Inspired by the power of molecular recognition in enzymatic processes, we sought to exploit its use in organic synthesis. Here we demonstrate how a synthetic rhodium-based catalyst can selectively bind a dehydroamino acid residue to initiate a sequential and stereoselective synthesis of cyclic peptides. Our combined experimental and theoretical study reveals the underpinnings of a cascade reduction that occurs with high stereocontrol and in one direction around a macrocyclic ring. As the catalyst can dissociate from the peptide, the C to N directionality of the hydrogenation reactions is controlled by catalyst–substrate recognition rather than a processive mechanism in which the catalyst remains bound to the macrocycle. This mechanistic insight provides a foundation for the use of cascade hydrogenations.
Amine hemilability enables boron to mechanistically resemble either hydride or proton Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 C. Frank Lee, Diego B. Diaz, Aleksandra Holownia, Sherif J. Kaldas, Sean K. Liew, Graham E. Garrett, Travis Dudding, Andrei K. Yudin
Tetracoordinate MIDA (N-methyliminodiacetic acid) boronates have found broad utility in chemical synthesis. Here, we describe mechanistic insights into the migratory aptitude of the MIDA boryl group in boron transfer processes, and show that the hemilability of the nitrogen atom on the MIDA ligand enables boron to mechanistically resemble either a hydride or a proton. The first case involves a 1,2-boryl shift, in which boron migrates as a nucleophile in its tetracoordinate form. The second case involves a neighbouring atom-promoted 1,4-boryl shift, in which boron migrates as an electrophile in its pseudo-tricoordinate form. Density functional theory studies and in situ NMR measurements all suggest that MIDA can act as a dynamic switch. These findings encouraged the development of novel migration processes involving boron that exploit the chameleonic behaviour of boron by acting as both a nucleophile and an electrophile, including the first report of a compound with a boronate functionality bound to carbon in the carboxylic acid oxidation state.
Direct α-alkylation of primary aliphatic amines enabled by CO2 and electrostatics Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 Juntao Ye, Indrek Kalvet, Franziska Schoenebeck, Tomislav Rovis
Primary aliphatic amines are important building blocks in organic synthesis due to the presence of a synthetically versatile NH2 group. N-functionalization of primary amines is well established, but selective C-functionalization of unprotected primary amines remains challenging. Here, we report the use of CO2 as an activator for the direct transformation of abundant primary aliphatic amines into valuable γ-lactams under photoredox and hydrogen atom transfer (HAT) catalysis. Experimental and computational studies suggest that CO2 not only inhibits undesired N-alkylation of primary amines, but also promotes selective intermolecular HAT by an electrostatically accelerated interaction between the in situ-generated negatively charged carbamate and the positively charged quinuclidinium radical. This electrostatic attraction overwhelms the inherent bond dissociation energies which suggest that HAT should occur unselectively. We anticipate that our findings will open up new avenues for amine functionalizations as well as selectivity control in HAT reactions.
Isolation, synthesis and bioactivity studies of phomactin terpenoids Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 Yusuke Kuroda, Karen J. Nicacio, Ildefonso Alves da Silva-Jr, Paul R. Leger, Stanley Chang, Juliana R. Gubiani, Victor M. Deflon, Nozomu Nagashima, Alexander Rode, Katherine Blackford, Antonio G. Ferreira, Lara D. Sette, David E. Williams, Raymond J. Andersen, Sonia Jancar, Roberto G. S. Berlinck, Richmond Sarpong
Studies of secondary metabolites (natural products) that cover their isolation, chemical synthesis and bioactivity investigation present myriad opportunities for discovery. For example, the isolation of novel secondary metabolites can inspire advances in chemical synthesis strategies to achieve their practical preparation for biological evaluation. In the process, chemical synthesis can also provide unambiguous structural characterization of the natural products. Although the isolation, chemical synthesis and bioactivity studies of natural products are mutually beneficial, they are often conducted independently. Here, we demonstrate the benefits of a collaborative study of the phomactins, diterpenoid fungal metabolites that serve as antagonists of the platelet activating factor receptor. Our isolation of novel phomactins has spurred the development of a bioinspired, unified approach that achieves the total syntheses of six congeners. We also demonstrate in vitro the beneficial effects of several phomactins in suppressing the rate of repopulation of tumour cells following gamma radiation therapy.
Broadband 2D IR spectroscopy reveals dominant asymmetric H5O2+ proton hydration structures in acid solutions Nat. Chem. (IF 26.201) Pub Date : 2018-07-30 Joseph A. Fournier, William B. Carpenter, Nicholas H. C. Lewis, Andrei Tokmakoff
Given the critical role of the aqueous excess proton in redox chemistry, determining its structure and the mechanism of its transport in water are intense areas of experimental and theoretical research. The ultrafast dynamics of the proton’s hydration structure has made it extremely challenging to study experimentally. Using ultrafast broadband two-dimensional infrared spectroscopy, we show that the vibrational spectrum of the aqueous proton is fully consistent with a protonated water complex broadly defined as a Zundel-like H5O2+ motif. Analysis of the inhomogeneously broadened proton stretch two-dimensional lineshape indicates an intrinsically asymmetric, low-barrier O–H+–O potential that exhibits surprisingly persistent distributions in both its asymmetry and O–O distance. This structural characterization has direct implications for the extent of delocalization exhibited by a proton’s excess charge and for the possible mechanisms of proton transport in water.
Publisher Correction: A new fundamental type of conformational isomerism Nat. Chem. (IF 26.201) Pub Date : 2018-07-27 Peter J. Canfield, Iain M. Blake, Zheng-Li Cai, Ian J. Luck, Elmars Krausz, Rika Kobayashi, Jeffrey R. Reimers, Maxwell J. Crossley
Publisher Correction: A new fundamental type of conformational isomerism Publisher Correction: A new fundamental type of conformational isomerism, Published online: 27 July 2018; doi:10.1038/s41557-018-0117-5 Publisher Correction: A new fundamental type of conformational isomerism
Microporous membranes comprising conjugated polymers with rigid backbones enable ultrafast organic-solvent nanofiltration Nat. Chem. (IF 26.201) Pub Date : 2018-07-23 Bin Liang, Hui Wang, Xinghua Shi, Baoying Shen, Xiao He, Zahid Ali Ghazi, Niaz Ali Khan, Haksong Sin, Abdul Muqsit Khattak, Lianshan Li, Zhiyong Tang
Conventional technology for the purification of organic solvents requires massive energy consumption, and to reduce such expending calls for efficient filtration membranes capable of high retention of large molecular solutes and high permeance for solvents. Herein, we report a surface-initiated polymerization strategy through C–C coupling reactions for preparing conjugated microporous polymer (CMP) membranes. The backbone of the membranes consists of all-rigid conjugated systems and shows high resistance to organic solvents. We show that 42-nm-thick CMP membranes supported on polyacrylonitrile substrates provide excellent retention of solutes and broad-spectrum nanofiltration in both non-polar hexane and polar methanol, the permeance for which reaches 32 and 22 l m−2 h−1 bar−1, respectively. Both experiments and simulations suggest that the performance of CMP membranes originates from substantially open and interconnected voids formed in the highly rigid networks.
Optimizing orthogonality Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 William S. C. Ngai, Peng R. Chen
Optimizing orthogonality Optimizing orthogonality, Published online: 20 July 2018; doi:10.1038/s41557-018-0115-7 A new pyrrolysyl-tRNA synthetase/PyltRNA (PylRS/PyltRNA) pair that is mutually orthogonal to existing PylRS/PyltRNA pairs has now been discovered and optimized. This system could enable the site-specific incorporation of a greater number of distinct non-conical amino acids into a protein.
The naked truth about K+ selectivity Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 Ben Corry
The naked truth about K+ selectivity The naked truth about K+ selectivity, Published online: 20 July 2018; doi:10.1038/s41557-018-0112-x Potassium channels rapidly move K+ ions across cell membranes while blocking Na+, but how these two effects are achieved simultaneously has remained unclear. Now, extensive molecular simulations show a single mechanism that features fully dehydrated ions can explain both rapid transport and impeccable selectivity.
Scissoring genes with light Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 Aleksandar P. Ivanov, Joshua B. Edel
Scissoring genes with light Scissoring genes with light, Published online: 20 July 2018; doi:10.1038/s41557-018-0116-6 Enzymes can perform various biological functions because of their delicately and precisely organized structures. Now, simple inorganic nanoparticles with a rationally designed recognition capability can mimic restriction enzymes and selectively cut specific DNA sequences.
Site-selective photoinduced cleavage and profiling of DNA by chiral semiconductor nanoparticles Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 Maozhong Sun, Liguang Xu, Aihua Qu, Peng Zhao, Tiantian Hao, Wei Ma, Changlong Hao, Xiaodong Wen, Felippe M. Colombari, Andre F. de Moura, Nicholas A. Kotov, Chuanlai Xu, Hua Kuang
Gene editing is an important genetic engineering technique that enables gene manipulation at the molecular level. It mainly relies on engineered nucleases of biological origin, whose precise functions cannot be replicated in any currently known abiotic artificial material. Here, we show that chiral cysteine-modified CdTe nanoparticles can specifically recognize and, following photonic excitation, cut at the restriction site GAT′ATC (′ indicates the cut site) in double-stranded DNA exceeding 90 base pairs, mimicking a restriction endonuclease. Although photoinduced reactive oxygen species are found to be responsible for the cleavage activity, the sequence selectivity arises from the affinity between cysteine and the conformation of the specific DNA sequence, as confirmed by quantum-chemical calculations. In addition, we demonstrate non-enzymatic sequence-specific DNA incision in living cells and in vivo using these CdTe nanoparticles, which may help in the design of abiotic materials for gene editing and other biological applications.
The realities of radium Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 Vikki Cantrill
The realities of radium The realities of radium, Published online: 20 July 2018; doi:10.1038/s41557-018-0114-8 Vikki Cantrill tells the story of element 88’s discovery and how its glowing reputation eventually faded.
Direct knock-on of desolvated ions governs strict ion selectivity in K+ channels Nat. Chem. (IF 26.201) Pub Date : 2018-07-20 Wojciech Kopec, David A. Köpfer, Owen N. Vickery, Anna S. Bondarenko, Thomas L. C. Jansen, Bert L. de Groot, Ulrich Zachariae
The seeming contradiction that K+ channels conduct K+ ions at maximal throughput rates while not permeating slightly smaller Na+ ions has perplexed scientists for decades. Although numerous models have addressed selective permeation in K+ channels, the combination of conduction efficiency and ion selectivity has not yet been linked through a unified functional model. Here, we investigate the mechanism of ion selectivity through atomistic simulations totalling more than 400 μs in length, which include over 7,000 permeation events. Together with free-energy calculations, our simulations show that both rapid permeation of K+ and ion selectivity are ultimately based on a single principle: the direct knock-on of completely desolvated ions in the channels’ selectivity filter. Herein, the strong interactions between multiple ‘naked’ ions in the four filter binding sites give rise to a natural exclusion of any competing ions. Our results are in excellent agreement with experimental selectivity data, measured ion interaction energies and recent two-dimensional infrared spectra of filter ion configurations.
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