Latest ArticlesA hydrogen bond-assisted α-selective glycosylation reaction by using 4, 6-dibenzyloxy-1, 3, 5-triazin-2-yl (DBT) β-glycosyl donors was developed for the efficient construction of 1, 2-cis-α-glycosidic bond in natural products. This method was applied successfully to the direct synthesis of complex oligosaccharide-derived glycolipids with simple protecting chemistry. Mechanistic studies using the NMR spectroscopy and DFT calculation provide a proof of concept for hydrogen bond-assisted glycosylation reaction towards α-specific construction of O-glycosidic linkage.
Liquid chromatography tandem mass spectrometry (LC-MS/MS) plays an important role in clinical diagnostics. Although LC-MS/MS is superior in terms of accurately quantifying molecules in complex matrices, instrument footprint, operation and maintenance complexity also hinder its expansion as the analytical technique of choice. In this study, a compact LC-MS instrument was developed, in which an assembled liquid chromatograph was coupled with a miniature ion trap mass spectrometer. The overall instrument has a footprint of 69 cm × 31 cm × 31 cm, and it requires no gas supply as well as minimum maintenance. Furthermore, the use of LC-MS is in accord with conventional clinical diagnostic protocols, and the choice of ion trap offers tandem MS performance. The results showed that the use of LC could improve both mixture analysis capability and detection sensitivity of the miniature mass spectrometer. After optimization, feasibility of this instrument in clinical practice was demonstrated by the quantitation of four widely used immunosuppressants in blood samples. Relatively good linearities were obtained, which spanned the reference ranges of effective therapeutic concentrations of each immunosuppressant. Intra-day and inter-day accuracy and precision of analytical method were also assessed. This work showed that a compact LC-MS instrument could be used in clinical diagnosis, either to replace conventional lab-scale instruments or to be used in POCT applications.
Gel polymer electrolytes (GPEs) are considered to be one most promising alternative to liquid electrolytes due to their suitability for creating safe and durable solid-state lithium-metal batteries. However, the mechanical properties of GPEs usually deteriorate dramatically when polymer matrices are plasticized by a liquid electrolyte, which leads to significant loss of battery performance. Therefore, the long-term structural integrity and good mechanical strength are critical characteristics of GPEs designed for high-performance batteries. Here, an ecologically compatible cellulose-based GPE with a crosslinked structure is synthesized via a facile and effective thiol-ene click chemistry method. The prepared thiol-ene crosslinked GPE possesses enhanced mechanical strength (10.95 MPa) and rigid structure, which enabled us to fabricate LiFePO4|Li batteries with ultra-long cycling performance. The capacity retention of the crosslinked cellulose-based GPE can be up to 84% at 0.5 C, even after 350 cycles, which is considerably higher than that of non-crosslinked GPE for which rapid decline in capacity occurs after 200 cycles. In addition, a GPE preparation method described in this work compares favorably well with existing commercial electrolytes for lithium metal batteries.
Nineteen diterpenoids, including saldigitin A (1) bearing an unprecedented 10-methylated 6/7/6 carbon ring system, two new icetexanes (2, 3), and two new nor-abietanes (5, 6) were characterized from the roots of Salvia digitaloides. Their structures were elucidated by the analysis of the spectroscopic data, X-ray crystallography, and TDDFT calculations of ECD spectra. The novel architecture of 1 should be biogenetically derived through the cleavage and re-cyclization of the B/C rings from the normal abietane skeleton. Biologically, 1–5 exhibited noticeable inhibitions on Cav3.1 low voltage-gated Ca2+ channel (LVGCC), with IC50 values in the range of 3.43–11.70 µmol/L. They are the first example of diterpenoids with 6/7/6 carbon rings system as Cav3.1 antagonists.
Control of self-assembly is significant to the preparation of supramolecular materials, but the control of hydration, responsiveness, dimension, catalysis of macrocyclic amphiphiles in an atom-economic manner is still a great challenge. The herein presented 527 Da low-molecular-weight macrocyclic amphiphile was fabricated by utilizing the selenium-containing crown ether as a hydrophobic motif together with guanidinium group as the hydrophilic moiety. The resulting benzo[21]crown-7 based macrocyclic amphiphile readily forms a redox-responsive solid nanoparticles in water, which can further interconnect into wrinkled pattern on-surface, as well as exhibits as a nanozyme for catalyzing disulfid bond formation. The present work highlights the great potential of guanidinium- and selenium-containing crown ethers for the control of functional assemblies.
Stimuli-responsive macrocycles are of importance for synthetic chemistry and smart materials. In this manuscript, we report two novel organoborane cyclophanes, which were successfully synthesized by ruthenium-catalyzed olefin metathesis. They are composed of one/two boron-doped helicene π-skeletons and flexible alkyl chain linkers, thus representing a new kind of non-conjugated organoborane macrocycles. Their cyclic structures and photophysical properties, as well as Lewis acidity were theoretically and experimentally investigated. Notably, two enantiomers in one single crystal are observed for one organoborane cyclophane, owning to the presence of helical π-framework in its cyclic structure. Moreover, their Lewis acid-base adducts may dissociate in the excited state and thus display intriguing photo-responsive fluorescence properties, which can be further modulated by temperature. This study thus provides a novel design strategy for non-conjugated organoborane macrocycles, which may promote the development of stimuli-responsive macrocyclic materials with fascinating properties.
Cyclin-dependent kinases (CDKs) have become potential targets for treating various diseases, especially cancer. Compound iCDK9 is an excellent and selective CDK9 inhibitor, but its major limitation is the potential toxicity and poor understanding of the underlying mechanism. The PROTAC (proteolysis targeting chimera) degraders of bioactive molecules can significantly induce in vitro and in vivo degradation of their target protein with high selectivity and effectively reduce the dose-limiting toxicity of small molecule drugs. Therefore, we designed and synthesized the bifunctional PROTAC molecules of iCDK9, being used for identifying its previously unknown target and revealing the underlying pharmacological mechanism. The PROTAC bifunctional molecule CD-5 could selectively and significantly degrade CDK9 with low cell toxicity. Therefore, we selected CD-5 as a chemical prober in the SILAC quantitative proteomic analysis, which disclosed that CD-5 could enormously lessen the lysine acetyltransferase KAT6A. Furthermore, KAT6A degradation induced by CD-5 repressed the levels of H3K14Ac and H3K23Ac. Lastly, the streptavidin immunoprecipitation (IP) assay confirmed a direct interaction between KAT6A and iCDK9. Collectively, our results uncover that KAT6A is a potential non-kinase target of iCDK9. Notably, this study also demonstrates that the PROTAC-SILAC strategy is an alternative approach for cellular target identification of bioactive molecules.
On-resin peptide modification renders an easy-to-operate method that combines solid-phase peptide synthesis efficiency and avoids tedious purification procedures. Herein, we report the transition-metal-free and redox-neutral approach for solid-phase Met diversification with substrate diversity, which could be applied to synthesize cyclic peptides of different sizes.
MoS2 is a typical electrocatalyst for hydrogen evolution reaction (HER), but the HER activity is spoilt by intensive adsorption towards H*, which requires further improvement. For n-type MoS2, the construction of p-n heterojunction with p-type MoO3 can reverse this situation, because inner electronic field in p-n heterojunction can facilitate H* desorption. Based on this hypothesis, p-n heterojunction is built between MoS2 and MoO3 with polyoxometalate compound as precursor. The obtained MoO3/MoS2 exhibits excellent HER activity, which only requires 68 mV to obtain 10 mA/cm2. With MoO3/MoS2 as cathode material and Zn slice as anode, Zn-H+ battery is assembled. Its open circuit voltage achieves 1.11 V with short circuit current 151.4 mA/cm2. The peak power density of this Zn-H+ battery reaches 47.6 mW/cm2. When discharge at 10 mA/cm2, the specific capacity and energy density reach 728 mAh/g and 759 Wh/kg. In this process, H2 production rate of Zn-H+ battery achieves 364 μmol/h with Faradic efficiency 97.8%. It realizes H2 production and electricity generation simultaneously.
As a burgeoning research field, ultrasound-responsive materials have attracted intense interest in healthcare research. However, the basic mechanism of sonochemical effect in the quasi-solid state is far from being well understood than those in the solution. Herein, we showcase mechanochemical transformations of europium(Ⅲ) complexes in a supramolecular hydrogel matrix. With the combination of labile terpyridine-europium complexes (TPY-Eu3+) as mechanochromic moieties and an ultrasound-responsive fluorogen (URF) as a molecular tweezer, the hydrogel produces a notable fluorescence change in response to ultrasound. The mechanochemical transformation was elucidated by molecular dynamics (MD) simulations, and fully probed and evidenced by electrochemical experiments, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy.
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