Nature Chemistry. doi:10.1038/nchem.2758
Authors: Felix J. Rizzuto & Jonathan R. Nitschke
An interconverting system of three distinct stereoisomers of a cuboctahedral CoII-based cage is able to regulate the binding affinities of large anionic guests. Through cooperative templation with fullerene guests, the cage converts into a desymmetrized cage that in turn exhibits positive cooperativity in binding of an icosahedral anion; this interaction is anti-cooperative in the fullerene-free parent.
Exploding class: Propellanes are a unique class of compounds with well over 10 000 members having inverted tetrahedral carbon atoms at their bridgehead positions that are linked through a weak single bond. These propeller-type compounds are not only structurally interesting, they also exhibit unusual reactivities. This Review highlights their syntheses and applications in material sciences, natural product synthesis, and medicinal chemisty.
[Review]
Alicia M. Dilmaç, Eduard Spuling, Armin de Meijere, Stefan Bräse
Angew. Chem. Int. Ed., April 06, 2017, https://doi.org/10.1002/anie.201603951 Read article
Nanohoops propel ahead: A triptycene-based molecular propeller with three nanohoop blades was synthesized by a three-fold intramolecular bisboronate homocoupling and subsequent reductive aromatization. Such nanopropeller molecules pack into a lamellar hexagonal structure with 11 Å-diameter channels that run perpendicularly to the layers.
[Communication]
Penghao Li, Lev N. Zakharov, Ramesh Jasti
Angew. Chem. Int. Ed., April 04, 2017, https://doi.org/10.1002/anie.201700935 Read article
Critically discussing and, if necessary, questioning results presented by other researchers has always been a vitally important process in science. Only through fruitful discourse does science arrive at broadly accepted hypotheses that finally become what we accept as scientific truth. In the spirit of this time-honored tradition, we have examined the crystal structure as well as X-ray diffraction data of the proposed compound [K(crypt-222)]+CF3−, which has recently been published. We arrived at the conclusion that the claim of the authors to have successfully and unambiguously characterized the ionic [K(crypt-222)]+CF3− through single-crystal X-ray diffraction is not sustainable. Even though it is possible that the original authors have indeed encountered the proposed species, the purpose of this report is to point out that the original authors cannot use the presented crystallographic data and model as proof for the existence of [K(crypt-222)]+CF3−. The reason for our conclusion is two-fold: firstly, the crystal structure was not refined to established standards of good crystallographic practice and secondly, even if best practices of structure determination are employed, the submitted diffraction data do not allow establishing conclusively the true nature of the compound at hand. Recognizing that this gives charge unbalance we have not resolved, we nevertheless suggest an alternative molecular model, [K(crypt-222)]⋅CHF3, to demonstrate the ambiguity of the diffraction data submitted by the original authors. However, because of this ambiguity, it is important to point out that the purpose of this report is not (and cannot be) the determination of the true nature of the compound at hand; we would merely like to demonstrate that an alternative interpretation of the original diffraction data is possible and, hence, that the conclusion drawn by the original authors is not unambiguously supported by their own data.
Playing devil's advocate: The recently published crystal structure of [K(crypt-222)]+CF3− is put to the test and its scientific impact is evaluated by a comparison with the alternative refinement model of [K(crypt-222)]⋅CHF3.
Na+ is one of the top analytes in the life sciences. Therefore, the development of easily accessible and highly Na+ selective fluorescent tools to monitor extra- or intracellular Na+ levels by fluorescence enhancement is still a challenge. Here, we report easily synthesizable fluorescent probes for Na+ made by “click” chemistry. These fluorescent probes show tunable fluorescence emission wavelengths, dissociation constants, and different Na+/K+ selectivities in CH3CN and H2O. More information can be found in the Full Paper by H.-J. Holdt et al. (DOI: 10.1002/chem.201605986).
Size does not matter: Nonribosomal peptides (NRPs) are assembled by large multienzyme machineries and represent a structurally highly diverse class of natural products with various bioactivities. This Review provides a thorough overview of NRPs, including their bioactivities, biosynthesis pathways, and their structural variation through biocombinatorial approaches.
[Review]
Roderich D. Süssmuth, Andi Mainz
Angew. Chem. Int. Ed., March 21, 2017, https://doi.org/10.1002/anie.201609079 Read article
Nature Nanotechnology. doi:10.1038/nnano.2017.44
Author: Chenfeng Ke
An organogel is made of molecular motors and modulators that act cooperatively to perform a full mechanical cycle of contraction and expansion at the macroscale.
Nature Nanotechnology. doi:10.1038/nnano.2017.28
Authors: Justin T. Foy, Quan Li, Antoine Goujon, Jean-Rémy Colard-Itté, Gad Fuks, Emilie Moulin, Olivier Schiffmann, Damien Dattler, Daniel P. Funeriu & Nicolas Giuseppone
A current challenge in the field of artificial molecular machines is the synthesis and implementation of systems that can produce useful work when fuelled with a constant source of external energy. The first experimental achievements of this kind consisted of machines with continuous unidirectional rotations and translations that make use of ‘Brownian ratchets’ to bias random motions. An intrinsic limitation of such designs is that an inversion of directionality requires heavy chemical modifications in the structure of the actuating motor part. Here we show that by connecting subunits made of both unidirectional light-driven rotary motors and modulators, which respectively braid and unbraid polymer chains in crosslinked networks, it becomes possible to reverse their integrated motion at all scales. The photostationary state of the system can be tuned by modulation of frequencies using two irradiation wavelengths. Under this out-of-equilibrium condition, the global work output (measured as the contraction or expansion of the material) is controlled by the net flux of clockwise and anticlockwise rotations between the motors and the modulators.
Total synthesis of mycobacterial arabinogalactan containing 92 monosaccharide units
Nature Communications, Published online: 16 March 2017; doi:10.1038/ncomms14851
Due to the vast number of potential isomers, the chemical synthesis of large carbohydrates is challenging. Here the authors report the synthesis of mycobacterial arabinogalactan, a biologically important natural product composed of 92 monosaccharide units, the largest synthetic polysaccharide to date.
A pH-gated dimer of bis(melamine)-substituted bispidine is reported (see picture). It is an efficient cotransporter of H+/Cl− across the lipid bilayer membrane.
[Communication]
Sopan Valiba Shinde, Pinaki Talukdar
Angew. Chem. Int. Ed., March 09, 2017, https://doi.org/10.1002/anie.201700803 Read article
Complexity is no longer a problem: A model-free isotopomer analysis of 13C-enriched biological cell extracts has been developed. The combination of NMR and MS data in a single analysis enables a highly specific and accurate determination of 13C isotopomers from a complex mixture of metabolites, which can be used for the interpretation of metabolic pathways.
[Communication]
Mei Chong, Anusha Jayaraman, Silvia Marin, Vitaly Selivanov, Pedro R. de Atauri Carulla, Daniel A. Tennant, Marta Cascante, Ulrich L. Günther, Christian Ludwig
Angew. Chem. Int. Ed., March 08, 2017, DOI: 10.1002/anie.201611634. Read article
Made into ribbons: Helicene-like graphene nanoribbons (HGNR) have been prepared through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction from a polychlorinated polyphenylene precursor.
[Communication]
Maxime Daigle, Dandan Miao, Andrea Lucotti, Matteo Tommasini, Jean-François Morin
Angew. Chem. Int. Ed., March 07, 2017, DOI: 10.1002/anie.201611834. Read article
Evidence for early life in Earth’s oldest hydrothermal vent precipitates
Nature 543, 7643 (2017). doi:10.1038/nature21377
Authors: Matthew S. Dodd, Dominic Papineau, Tor Grenne, John F. Slack, Martin Rittner, Franco Pirajno, Jonathan O’Neil & Crispin T. S. Little
Although it is not known when or where life on Earth began, some of the earliest habitable environments may have been submarine-hydrothermal vents. Here we describe putative fossilized microorganisms that are at least 3,770 million and possibly 4,280 million years old in ferruginous sedimentary rocks,
Evolution: How humans adapt to arsenic
Nature 543, 7643 (2017). doi:10.1038/543009b
People living in Chile's Atacama Desert have different versions of a gene that allow them to cope with the region's naturally high levels of arsenic.Arsenic from rocks seeps into the desert's scarce water sources, exposing people in the Camarones Valley to levels 100 times
Nature Chemistry. doi:10.1038/nchem.2737
Authors: Chenrui Chen, Junjun Tan, Ming-Chien Hsieh, Ting Pan, Jay T. Goodwin, Anil K. Mehta, Martha A. Grover & David G. Lynn
Di- and tripeptide building blocks in which the C-terminus has been converted into an aldehyde are shown to form dynamic chemical networks through imine condensation followed by the formation of cyclic N,N-acetals. The networks exhibit multi-phase growth of prion-like assemblies that template the formation of chain-length-specific peptide-like oligomers.
Nature Chemistry. doi:10.1038/nchem.2738
Authors: Tolulope O. Omosun, Ming-Chien Hsieh, W. Seth Childers, Dibyendu Das, Anil K. Mehta, Neil R. Anthony, Ting Pan, Martha A. Grover, Keith M. Berland & David G. Lynn
Simple peptides are shown to assemble into well-defined amyloid phases with paracrystalline surfaces that can catalyse reactions in an enantioselective manner. Modifying individual amino acids in the building blocks enables the structure of the assembled aggregates, and the reactions that they can catalyse, to be controlled predictably.
