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  • Dunlap Crane posted an update 2 days, 7 hours ago

    New Zealand manuka honeys are known for their propensity to increase apparent C4 sugar content during storage. Depending on the particular storage regime and the initial content of dihydroxyacetone (DHA) in honey, the ready-to-market product often fails the C4 sugar test because of the above phenomenon. We have used DHA labeled with a radioactive 14C isotope in a set of honeys subject to an incubation experiment. These honeys were analyzed for DHA, methylglyoxal (MG), hydroxymethylfurfural (HMF), apparent C4 sugars, and 14C scintillation counts over a period of 18 months. The major conclusion of this experiment is that neither DHA nor MG is responsible for the δ13C shift in the honey protein extract. There must be some other yet unknown substance of manuka honey, which binds to the protein and causes negative δ13C shift. One identified candidate for such a binding is carbon dioxide.Differentially selective molecular sensors that exhibit differential response toward multiple analytes are cost-effective and in high demand for various practical applications. A novel, highly differentially selective electrochemical and fluorescent chemosensor, 5, based on a ferrocene-appended coumarin-quinoline platform has been designed and synthesized. Our designed probe is very specific toward Fe3+ via a reversible redox process, whereas it detects Cu2+ via irreversible oxidation. Interestingly, it exhibits differential affinity toward the Cu+ ion via complexation. High-resolution mass spectrometry, 1H NMR titration, and IR spectral studies revealed the formation of a bidentate Cu+ complex involving an O atom of the amide group attached to the quinoline ring and a N atom of imine unit, and this observation was further supported by quantum-chemical calculations. The metal binding responses were further investigated by UV-vis, fluorescence spectroscopy, and electrochemical analysis. Upon the addition of Fe3+ and Cu2+ ions, the fluorescence emission of probe 5 shows a “turn-on” signal due to inhibition of the photoinduced electron transfer (PET) process from a donor ferrocene unit to an excited-state fluorophore. The addition of sodium l-ascorbate (LAS) as a reducing agent causes fluorescence “turn off” for the Fe3+ ion because of reemergence of the PET process but not for the Cu2+ ion because it oxidizes the ferrocene unit to a ferrocenium ion with its concomitant reduction to Cu+, which further complexes with 5. Thermodynamic calculations using the Weller equation along with density functional theory calculations validate the feasibility of the PET process. A unique combination of Fe3+, LAS, and Cu2+ ions has been used to produce a molecular system demonstrating combinational “AND-OR” logic operation.Supramolecular hydrogels based on inclusion complexation between cyclodextrins (CDs) and polymers have attracted much interest because of their potential for biomedical applications. It is also attractive to incorporate stimuli-responsive properties into the system to create “smart” hydrogels. Herein, a poly(N-isopropylacrylamide) (PNIPAAm) star polymer with a β-CD core and an adamantyl-terminated poly(ethylene glycol) (Ad-PEG) polymer were synthesized. They self-assembled into a thermoresponsive pseudo-block copolymer through host-guest complexation and formed supramolecular micelles with the change in environment temperature. Subsequently, an injectable polypseudorotaxane-based supramolecular hydrogel was formed between α-CD and the PEG chains of the pseudo-block copolymer. The hydrogel had a unique network structure involving two types of supramolecular self-assemblies between cyclodextrins and polymers, that is, the host-guest complexation between β-CD units and adamantyl groups and the polypseudorotaxane carriers with DOX encapsulated in the hydrophobic core, achieving a better cellular uptake and anticancer effect than free DOX controls, even in multidrug-resistant cancer cells. According to these findings, the dual supramolecular hydrogel developed in this work with remarkable thermoresponsive properties might have potential for sustained anticancer drug delivery with enhanced therapeutic effect in multidrug-resistant cancer cells.A “two-state reactivity” scenario has been computationally disclosed for dinitrogen activation by a diniobium tetrahydride. Remarkably, it is revealed that alkali metal cations play a crucial role via alkali···N coordination interaction, which is capable of decreasing the activation barriers of N-H formation and subsequent H2 elimination in particular. Furthermore, the effect of various alkali metal cations has also been investigated systematically.New metal-organic frameworks (MOFs) based on flexible tetra-carboxylate ligands and Cu(II) are designed to gain stimuli-responsive materials. Unstable MOFs can be more stable with unabated flexibility by replacing coordinated solvent molecules with auxiliary N-based ligands. Two of them are intensively studied by in situ single-crystal X-ray diffraction (SCXRD) analysis and the unit cell parameters during transformations have been observed in detail. They undergo exceptional structural transformations which can be divided into two processes the thermal-responsive phase transition and the solvent-responsive phase transition. Sunitinib The thermal-responsive phase transition takes place in a narrow temperature interval reversibly. However, the solvent-responsive phase transition is a gradual and irreversible process. The stimuli-responsive mechanism has also been explored by comparing the parameters of the crystal structures under different temperatures. Fascinatingly, their exceptional structural transformations correlate with the flexibility of the ligand fragments and the [Cu2(RCOO)4] clusters.Field switching ion shutters allow generating short ion packets with high ion densities by first ionizing for several milliseconds in a field-free ionization region and then quickly pushing the entire ion population out into the drift region. Thus, they are an excellent choice for compact ion mobility spectrometers with both high resolving power and low limits of detection. Here, we present an improved setup, named the extended field switching ion shutter. By generating a second field-free region between the ionization region and the drift region, shielding of the ionization region is significantly improved, even when using grids with higher optical transparency to improve ion transmission into the drift region. Furthermore, it is shown that under certain conditions, ion transmission through multiple grids in series can even surpass transmission through a single grid of the same transparency. For the studied ions, the signal intensity at low concentrations increases by approximately a factor of 7 to 9 for protonated monomers, 10 to 14 for proton-bound dimers, and 25 for the proton-bound 1-octanol trimer compared to the classical field switching shutter.

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