Water‐Soluble Molecularly Imprinted Nanoparticles (MINPs) with Tailored,Functionalized, Modifiable Binding Pockets

Construction of receptors with binding sites of specific size, shape, and functional groups is important to both chemistry and biology. Covalent imprinting of a photocleavable template within surface–core doubly cross‐linked micelles yielded carboxylic acid‐containing hydrophobic pockets within the water‐soluble molecularly imprinted nanoparticles. The functionalized binding pockets were characterized by their binding of amine‐ and acid‐functionalized guests under different pH values. The nanoparticles, on average, contained one binding site per particle and displayed highly selective binding among structural analogues. The binding sites could be modified further by covalent chemistry to modulate their binding properties.     

Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes with diselenides and mCPBA

KBr or NaCl is found to be a good catalyst in Se-Se bond cleavage of diselenides in the present of the oxidant mCPBA. The electrophilic addition of the in situ generated reactive electrophilic selenium species PhSeX (X=Br, Cl) to alkenes in AcOH provides a convenient access to 2-acetoxy-1-selenides. Compared with other catalysts, KBr or NaCl is less expensive and more environment-friendly.     

Phase structure and crystallization behavior of polyethylene in its blends with cis-1,4-butadiene rubber

Phase structure and crystallization behavior of polyethylene(PE) in its blends with cis-1,4-butadiene rubber(BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 °C, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 °C, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.     

Flammability characterization and effects of magnesium oxide in halogen-free flame-retardant EVA blends

The effects of magnesium oxide(Mg O) on the flame retardant performance of intumescent systems based on ammonium polyphosphate(APP) and pentaerythritol(PER) in ethylene vinyl acetate copolymer(EVA) were studied. The results showed that Mg O affects both the quality and quantity of residual char. There is an optimal value for the loading amount of Mg O. More or less Mg O loading may cause the formation of defective char layers and worsen the flame retardancy of EVA. According to the results of limiting oxygen index(LOI), vertical flammability test(UL94 rating) and cone calorimetry(CONE), the best flame retardancy with a strong and well intumescent char is obtained from the sample with 1 wt% of Mg O, which has the highest LOI value of 27.9, UL94 rating of V-0 and the lowest peak heat release rate of 242 k W·m?2.     

Automated solvent system screening for the preparative countercurrent chromatography of pharmaceutical discovery compounds

A fully automated countercurrent chromatography system has been constructed to rapidly screen the commonly used heptane/ethyl acetate/methanol/water solvent system series and translate the results to preparative scale separations. The system utilizes “on‐demand” preparation of the heptane/ethyl acetate/methanol/water solvent system upper and lower phases. Elution‐extrusion countercurrent chromatography was combined with non‐dynamic equilibrium injection reducing the screening time for each heptane/ethyl acetate/methanol/water system to 17 min. The result enabled solvent system development to be reduced to under 2 h. The countercurrent chromatography system was interfaced with a mass spectrometer to allow selective detection of target components in crude medicinal chemistry reaction mixtures. Mass‐directed preparative countercurrent chromatography purification was demonstrated for the first time using a synthetic tetrazole epoxide derived from a routine medicinal chemistry support workflow.     

Determination of neuroprotective oxysterols in Calculus bovis,human gallstones,and traditional Chinese medicine preparations by liquid chromatography with mass spectrometry

So far, the components responsible for the neuroprotective effects of Calculus bovis are unclear. Cholesterol, one of the major components in Calculus bovis, is easily oxidized into oxysterols, which possess direct or indirect neuroprotective effects proved by our and others’ previous studies. Therefore, a liquid chromatography with mass spectrometry method coupled with ultrasonic extraction and solid‐phase extraction was developed for the determination of neuroprotective oxysterols in Calculus bovis, human gallstones, and traditional Chinese medicine preparations. Chromatographic separation was achieved on a C₁₈ column with isocratic elution at a flow rate of 1 mL/min. The established method showed good linearity (R² > 0.998), sensitivity with low limits of detection (0.06–0.39 μg/g), acceptable precisions (relative standard deviations ≤ 7.4%), stability (relative standard deviations ≤ 5.9%), and satisfactory accuracy (92.4–102.9%) for all analytes identified by different retention times, which could be applied for the determination of oxysterols. Five kinds of oxysterols proved to function as neuroprotectants were detected at different concentrations. Among them, 7β‐hydroxycholesterol and cholestane‐3β,5α,6β‐triol were rather abundant in the samples. It could be concluded that the potential neuroprotective components in Calculus bovis may be these oxysterols.