A bioactive new protostane-type triterpenoid from Alisma plantago-aquatica subsp. orientale (Sam.) Sam.

A new protostane-type triterpenoid, 5β,29-dihydroxy alisol A (1) was isolated from Alisma plantago-aquatica subsp. orientale (Sam.) Sam. as well as 12-deoxyphorbol-13α-pentadecanoate (2). We first report the presence of compound 2 in the genus Alisma. Their structures were established on the basis of 1D and 2D NMR, and HRESIMS spectroscopic analyses. All the isolated compounds were assayed for their inhibitory effects against human carboxylesterase 2 (HCE-2). Compounds 1 and 2 displayed inhibitory activities against HCE-2 with IC₅₀ values of 29.2 and 4.6 μM, respectively. The interaction mechanisms of HCE-2 with compounds 1 and 2 were investigated by molecular docking, respectively.     

Synthesis and Absorption Spectra of n‐Type Conjugated Polymers Based on Perylene Diimide

Two novel n‐type conjugated polymers based on perylene diimide (PDI), poly(PDI‐vinylene) (PDIV), and poly(PDI‐thienylene) (PDITh), have been designed and synthesized by the Stille coupling reaction. In comparison with the PDI monomer (compound M1), PDIV and PDITh films show a significantly broad absorption band from 380 to 720 nm, and a narrower bandgap of ≈1.71 and 1.74 eV, respectively. Cyclic voltammograms of the two polymers display a couple of reversible reduction/re‐oxidation (n‐doping/dedoping) peaks. The onset reduction (n‐doping) potentials of PDIV and PDITh are at −0.62 V and −0.66 V versus Ag/Ag⁺ respectively, which correspond to the electron affinities (EAs) of 4.09 eV for PDIV and 4.05 eV for PDITh. The EA values of the two polymers are the highest among the n‐type conjugated polymers reported to date. The results indicate that PDIV and PDITh could be used as polymer acceptors in all polymer solar cells.

     

Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine.     

A New Carotane Sesquiterpenoid Derivative with Antifungal Activity from Gymnopus sp. 0612-9

Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was...     

Stereodivergent Desymmetrization of Simple Dicarboxylates via Branch-Selective Pd/Cu Catalyzed Allylic Substitution

Asymmetric desymmetrization has been demonstrated to be a powerful strategy for building stereocenters in asymmetric synthesis. Herein, a Pd/Cu catalyzed asymmetric desymmetrization reaction with a simple geminal dicarboxylate is reported. A wide scope of imino esters bearing an aryl or heteroaromatic group were compatible with this bimetallic catalytic system. The reactions proceeded smoothly, giving the desired products in good yields with high to excellent regio-, diastereo-, and enantioselectivity (up to 20 : 1 branched:linear, >20 : 1 dr, >99 % ee). Notably, the reaction favored branched selectivity, which is unusual for the Pd-catalyzed allylic alkylation reaction. In addition, the standard product could be easily transformed to other valuable molecules such as chiral allylic alcohols, carbamates, and organic boron compounds. Furthermore, DFT calculations were conducted to explain the origin of the branched selectivity.     

Multiple bifurcations and local energy minimizers in thermoelastic martensitic transformations

Thermoelastic martensitic transformations in shape memory alloys can be modeled on the basis of nonlinear elastic theory.Microstructures of fine phase mixtures are local energy minimizers of the total energy.Using a one-dimensional effective model,we have shown that such microstructures are inhomogeneous solutions of the nonlinear Euler-Lagrange equation and can appear upon loading or unloading to certain critical conditions,the bifurcation conditions.A hybrid numerical method is utilized to calculate the inhomogeneous solutions with a large number of interfaces.The characteristics of the solutions are clarified by three parameters:the number of interfaces,the interface thickness,and the oscillating amplitude.Approximated analytical expressions are obtained for the interface and inhomogeneity energies through the numerical solutions.     

Synthesis and optical properties of poly(aryl ether ketone)s incorporating porphyrins in the backbones

A series of novel soluble poly(aryl ether ketone)s (PAEKs) based on 5,10‐bis(4‐hydroxyphenyl)?15,20‐diphenylporphyrin (cis‐DHTPP), 4,4′‐(hexafluoroisopropylidene) diphenol (6FBPA) and 4,4′‐difluorobenzophenone (DFB) were synthesized and characterized by FT‐IR, ¹H‐NMR, UV–vis and fluorescence spectroscopies. The intrinsic photophysical properties of porphyrins were preserved because of the absence of photoinduced electron transfer in the polymer chains. Investigation of the copolymers thermal properties indicated that these polymers had high glass transition temperatures and excellent thermal stabilities. The results of Z‐scan and optical limiting measurements manifested that incorporation of the porphyrin chromophore into the main chain engendered the novel PAEKs with superior nonlinear optical properties and optical limiting function, which could be effectively tuned by varying the molar ratio of porphyrin monomers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1282–1290     

Simultaneous determination of three dipeptides (JBP485, Gly–Sar and JBP923) in the cell lysates by liquid chromatography‐tandem mass spectrometry: application to identify the function of the PEPT1 transfected cell

A simple and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the simultaneous determination of JBP485, Gly–Sar and JBP923 in the cell lysates using methanol as a deproteinization solvent was developed and validated. Detection was performed by turbo ionspray ionization in multiple reaction monitoring mode using the transitions of m/z 147.1 → m/z 90.1 for Gly–Sar, m/z 201.1 → m/z 86.1 for JBP485, m/z 219.1 → m/z 86.1 for JBP923 and m/z 152.0 → m/z 110.0 for paracetamol (internal standard). The analytes were separated on a Hypersil ODS C₁₈ HPLC column using isocratic elution mode with a mobile phase containing 0.1% formic acid in water–methanol (97:3, v/v) at a flow rate of 0.2 mL/min. The calibration curves were demonstrated to be linear over the concentration range of 5.00?5000 nm with coefficient of 0.9968 for Gly–Sar, 0.9975 for JBP485 and 0.9952 for JBP923. The intra‐ and inter‐day precisions were <10.2% for each quality contro; level, and the accuracy was within ±5.6% for each analyte. The matrix effect, the extraction recovery and stabilities of LC‐MS/MS analysis were also investigated. This validated method was successfully applied to the simultaneous determination of JBP485, Gly–Sar and JBP923 in the cell lysates for identification of stably transfected HeLa cells with human PEPT1. Copyright © 2014 John Wiley & Sons, Ltd.     

CO<Subscript>2</Subscript>-responsive Polymeric Fluorescent Sensor with Ultrafast Response

Abstract Response speed is one of the most important evaluation criteria for CO₂ sensors. In this work, we report an ultrafast CO₂ fluorescent sensor based on poly[oligo(ethylene glycol) methyl ether methacrylate]-b-poly[N,N-diethylaminoethyl methacrylate-r-4-(2-methylacryloyloxyethylamino)-7-nitro-2,1,3-benzoxadiazole] [POEGMA-b-P(DEAEMA-r-NBDMA)], in which DEAEMA units act as the CO₂-responsive segment and 4-nitrobenzo-2-oxa-1,3-diazole (NBD) is the chromophore. The micelles composed of this copolymer could disassemble in 2 s upon CO₂ bubbling, accompanying with enhanced fluorescence emission with bathochromic shift. Furthermore, the quantum yield of the NBD chromophore increases with both the CO₂ aeration time and the NBD content. Thus we attribute the fluorescent enhancement to the inhibition of the photo-induced electron transfer between unprotonated tertiary amine groups and NBD fluorophores. The sensor is durable although it is based on “soft” materials. These micellar sensors could be facilely recycled by alternative CO₂/Ar purging for at least 5 times, indicating good reversibility.     

ZnO-rich CdS-ZIF-8 catalyst for enhanced visible-light photocatalytic degradation of methylene blue

CdS-ZIF-8 photocatalyst was prepared by introducing a ZnO-rich zeolitic imidazolate framework-8 (ZIF-8) during synthesis of CdS by a facile solvothermal method, using ZnO-rich ZIF-8 and cadmium acetate [Cd(Ac)₂] as support and CdS precursor, respectively. The introduction of ZnO-rich ZIF-8 and the photodegradation performance of the catalyst for methylene blue (MB) organic dye were systemically investigated. The CdS-ZIF-8 catalysts were also characterized using X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy, N₂ adsorption–desorption measurements, Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy. The results indicated that CdS-ZIF-8 contained ZIF-8, CdS, and ZnO phases. The CdS in CdS-ZIF-8 catalysts exhibited smaller particle size compared with pure CdS. Furthermore, compared with pure CdS, CdS-ZIF-8-30 with introduction of ZnO-rich ZIF-8 exhibited higher surface area (77.3 m²/g) and pore volume (0.103 cm³/g). EDX and FT-IR results suggested that a CdS/ZnO heterostructure was formed, which effectively reduced recombination of photogenerated electron–hole pairs. Radical trapping experimental data and band edge position analysis revealed that Z-scheme behavior also played a role in the system. Relying on the combined effect of their structure, the photodegradation efficiency of all the CdS-ZIF-8 catalysts was obviously superior to that of pure CdS for degradation of MB under visible-light irradiation. Photodegradation results illustrated that CdS-ZIF-8 with introduction of 30 mg ZnO-rich ZIF-8 (denoted as CdS-ZIF-8-30) exhibited optimal photodegradation activity.