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  • Song Wade posted an update 20 hours, 6 minutes ago

    Using solid-state 15N NMR spectroscopy, the cis/trans isomerization in a 2-D array of surface-mounted azobenzene-based switches was detected for the first time. In order to achieve this, a new class of rod-shaped molecular switches, suitable for formation of two-dimensional regular arrays on large facets of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) nanocrystals, was synthesized. A mechanochemical approach was used to prepare corresponding host-guest surface inclusions in a TPP matrix. Comparison of thermal steps in solution and supramolecular surface inclusions revealed that switching of individual molecules is not compromised by the close proximity of neighbours.This article describes the design, synthesis, and analysis of a new class of polymer that is capable of depolymerizing continuously, completely, and cleanly from head to tail when a detection unit on the head of the polymer is exposed to a specific applied signal. The backbone of this polymer consists of 1,3-disubstituted pyrroles and carboxy linkages similar to polyurethanes. Diverse side chains or reactive end-groups can be introduced readily, which provides modular design of polymer structure. The designed depolymerization mechanism proceeds through spontaneous release of carbon dioxide and azafulvene in response to a single triggering reaction with the detection unit. These poly(carboxypyrrole)s depolymerize readily in non-polar environments, and even in the bulk as solid-state plastics.The Ca2+ release-activated Ca2+ (CRAC) channels control many Ca2+-modulated physiological processes in mammals. Hyperactivating CRAC channels are known to cause Stormorken syndrome. Here we show the design of azopyrazole-derived photoswitchable CRAC channel inhibitors (designated piCRACs), which enable optical inhibition of store-operated Ca2+ influx and downstream signaling. Moreover, piCRAC-1 has been applied in vivo to alleviate thrombocytopenia and hemorrhage in a zebrafish model of Stormorken syndrome in a light-dependent manner.Two skeletally novel tetracyclic diterpenoids, psathyrins A (1) and B (2), have been characterized from cultures of the basidiomycete Psathyrella candolleana. Their structures including absolute configurations were established by means of spectroscopic methods, as well as ECD calculations. They possess a novel 5/5/4/6-fuesd ring system, for which the biosynthetic pathway is proposed. Compounds 1 and 2 inhibited the growth of Staphylococcus aureus and Salmonella enterica.A molecule-based ferroelectric triethylmethylammonium tetrachloroferrate(III) ([N(C2H5)3CH3][FeCl4]) powder was designed as a multifunctional material exhibiting excellent multiple bistability. Prepared by the slow evaporation method at room temperature, the compound crystallizes in the non-centrosymmetric assembly of hexagonal symmetry (P63mc space group) which undergoes a reversible temperature-triggered phase transition pinpointed at 363 K to the centrosymmetric packing within the P63/mmc space group. Aside from the inseparable role of the symmetry-breaking process smoothly unveiled from the X-ray powder diffraction data, a striking change in the dielectric permittivity observed during the paraelectric-to-ferroelectric phase transition directly discloses the bistable dielectric behavior-an exceptionally high increase in the dielectric permittivity of about 360% at 100 kHz across the heating and cooling cycles is direct proof showing the highly desirable stimuli-responsive electric ordering in this improper ferroelectric architecture. Due to the magnetically modulated physical properties resulting in the coupling of magnetic and electric orderings, the flexible assembly of [N(C2H5)3CH3][FeCl4] could be used to boost the design and development of novel magnetoelectric devices.An efficient divergent synthetic strategy that leverages the natural product spectinomycin to access uniquely functional-ized monosaccharides is described. Stereoselective 2′- and 3′-reduction of key spectinomycin-derived intermediates ena-bled facile access to all eight possible 2,3-stereoisomers of 4,6-dideoxyhexoses as well as representative 3,4,6-trideoxysugars and 3,4,6-trideoxy-3-aminohexoses. In addition, the method was applied to the synthesis of two function-alized sugars commonly associated with macrolide antibiotics – the 3-O-alkyl-4,6-dideoxysugar D-chalcose and the 3-N-alkyl-3,4,6-trideoxysugar D-desosamine.The incorporation of molecular switches in organic structures is of great interest in the chemical design of stimuli-responsive materials that mimic the complex functions of living systems. Merocyanine dyes that convert to spiropyran moieties upon exposure to visible light have been extensively studied as they can be incorporated in hydrated covalent networks that will expel water when this conversion occurs and induce a volumetric shrinkage. We report here on a sulfonate-based water-soluble photoswitch that, in contrast to the well-known systems, triggers a volumetric expansion in hydrogels upon exposure to photons. Contraction is in turn observed under dark conditions in a highly reversible manner. The novel behavior of the photoswitch incorporated in the covalent network was predicted by coarse-grained simulations of the system’s chemical structure. Using pH control and polymeric structures that differ in lower critical solution temperature, we were able to develop hydrogels with highly tunable volumetric expansion. The novel molecular function of the systems developed here led to materials with the negative phototaxis observed in plants and could expand the potential use of hydrogels as sensors, soft robots, and actuators.Glyphosate is the most used herbicide on the planet because of its excellent efficacy on almost all weeds species and due to the large-scale adoption of transgenic, glyphosate-resistant (GR) crops. Agnes Rimando became an expert in glyphosate analysis almost 20 years ago to support research on GR crop safety and on mechanisms of evolved glyphosate resistance by weeds. Her work was the first to show that the amount of glyphosate and its primary metabolite aminomethylphosphonic acid (AMPA) that accumulates in GR soybean seed from plants treated with approved glyphosate doses can approach their legal limits. Nec-1s molecular weight However, she later found that the only trace amounts of these compounds accumulate in seed of GR maize treated with recommended glyphosate doses. She showed that GR canola, the only transgenic crop with a transgene encoding an enzyme for degradation of glyphosate, metabolizes glyphosate to AMPA very rapidly. Her work was instrumental in providing support for the view that “yellow flash” symptoms sometimes observed in field-grown GR soybeans are due to accumulation of enough AMPA to cause mild phytotoxicity.

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