Simulation of nuclide migration in a middle- and low-level radioactive waste repository based on GMS

Journal of Radioanalytical and Nuclear Chemistry - Groundwater is the most important factor contributing to the diffusion and migration of radionuclides in the repository. In this paper, the...     

Fractionated Crystallization Kinetics and Polymorphic Homocrystalline Structure of Poly(L-lactic acid)/Poly(D-lactic acid) Blends: Effect of Blend Ratio

Stereocomplex (SC) crystallization has been an effective way to improve the physical performances of stereoregular polymers. However, the competition between homo and SC crystallizations can lead to more complicated crystallization kinetics and polymorphic crystalline structure in stereocomplexable polymers, which influences the physical properties of obtained materials. Herein, we select the medium-molecular-weight (MMW) poly(_L-lactic acid)/poly(_D-lactic acid) (PLLA/PDLA) asymmetric blends with different PDLA fractions (f_D=0.01–0.5) as the model system and investigate the effects of f_D and crystallization temperature (T_c) on the crystallization kinetics and polymorphic crystalline structure. We observe the fractionated (i.e., multistep) crystallization kinetics and the formation of peculiar β-form homocrystals (HCs) in the asymmetric blends under quiescent conditions, which are strongly influenced by both f_D and T_c. Precisely, crystallization of β-form HCs is favorable in the MMW PLLA/PDLA blends with high f_D (≥0.2) at a low T_c (80–100 °C). It is proposed that the formation of metastable β-form HCs is attributed to the conformational matching between β-form HCs and SCs, and the stronger constrain effects of precedingly-formed SCs in the early stage of crystallization. Such effects can also cause the multistep crystallization kinetics of MMW PLLA/PDLA asymmetric blends in the heating process.

     

过渡金属催化的1,2,3-三氮唑导向的C—H键官能团化反应研究进展

1,2,3-三氮唑化合物是一类具有重要生理活性的含氮杂环化合物, 其在医药、农药、材料科学等领域都具有广泛的应用. 不断开发基于三氮唑骨架的新型结构, 寻找新型高效的合成三氮唑衍生物的方法具有重要的意义和应用价值. 过渡金属催化的C—H键活化策略具有操作简便、效率高、三废少等优点, 是现代有机合成中高效构筑C—C键和C—X键的强大工具. 近年来, 过渡金属催化的三氮唑导向的C—H官能团化反应受到科学工作者的广泛关注, 该方法以不同结构的1,2,3-三氮唑作为导向基团, 在不同反应条件下通过直接活化C—H键来构建新的C—C键和C—X键, 高效合成复杂的三氮唑衍生物. 综述了近年来1,2,3-三氮唑导向下过渡金属催化的C—H键官能团化反应研究进展, 按照成键类型(碳-碳键、碳-杂键以及环化反应)对这些反应进行了梳理和总结, 并对今后该领域的发展进行了展望.     

Highly porous CuO/MnO2 catalyst prepared by gas release-assisted technology and its enhancement of formaldehyde removal efficiency

Research on Chemical Intermediates - A porous CuO/MnO2 catalyst was synthesized by a gas release-assisted method. Due to the participation of gases (H2O, NH3, CO2) released from ammonia and...     

On the force field optimisation of $$\beta$$ β -lactam cores using the force field Toolkit

Journal of Computer-Aided Molecular Design - When employing molecular dynamics (MD) simulations for computer-aided drug design, the quality of the used force fields is highly important. Here we...     

Density functional theory study on the reaction mechanism of Ni+-catalysed cyclohexane dehydrogenation

Structural Chemistry - A detailed theoretical analysis of the mechanism of chemical bond activation in cyclohexane catalysed by the atomic transition-metal cation Ni+ was performed by density...     

Fabrication and characterization of glutathione-responsive nanoparticles from the disulfide bond-bridged block copolymer

The purpose of this paper is to fabricate novel nanoparticles (NPs) from a single disulfide bond-bridged block copolymer poly(hydroxyethyl methacrylate)-S-S-polycaprolactone (PHEMA-S-S-PCL). The novel biomaterial was synthesized by ring-opening polymerization and reversible addition–fragmentation chain transfer polymerization. The cargo-free NPs were fabricated with the solvent evaporation method, and studies on NPs' characterizations were carried out. The hydrogen nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy spectra confirmed the synthesis of PHEMA-S-S-PCL copolymer. Thermo-gravimetric analysis curves indicated that the obtained PHEMA-S-S-PCL copolymer had good thermostability. Transmission electron microscopy and dynamic light scatter results suggested that the cargo-free NPs were in round shapes with an average diameter of 103.6 ± 0.12 nm. The low critical micelle concentration of cargo-free NPs (7.9 × 10^?4 mg/ml) indicated that these NPs would keep their spherical shapes after being attenuated by abundant liquid (e.g., blood or body fluid). Furthermore, these NPs showed high stability at the presence of bovine serum albumin. Therefore, it could be speculated that these NPs would not be absorbed by proteins in blood, and they could be used as a candidate carrier for drug delivery.     

Spatiotemporally-regulated multienzymatic polymerization endows hydrogel continuous gradient and spontaneous actuation

There are several natural materials which have evolved functional gradients,ingeniously attaining maximal efficacy from limited components.Herein,we utilized the spatiotemporal distribution of initiator acetylacetone to regulate the multienzyme polymerization and fabricate a chitosan-polymer hydrogel.The temporal priority order of acetylacetone was higher than phenolmodified chitosan by density functional theory calculation.The acetylacetone within the gelatin could gradually diffuse spatially into the chitosan hydrogel to fabricate the composite hydrogel with gradient network structure.The gradient hydrogel possessed a transferring topography from the two-dimensional pattern.A continuously decreased modulus along with acetylacetone diffusion was confirmed by atomic force microscope-based force mapping experiment.The water-retaining ability of various regions was confirmed by low-field nuclear magnetic resonance(NMR)and thermogravimetric analysis(TG)analysis,which led to the spontaneous actuation of gradient hydrogel with maximum 1821°/h curling speed and 227°curling angle.Consequently,the promising gradient hydrogels could be applied as intelligent actuators and flexible robots.     

An efficient strategy based on two-stage chromatography and in vitro evaluation for rapid screening and isolation of acetylcholinesterase inhibitors from Scutellaria baicalensis Georgi

The extraction of Scutellaria baicalensis Georgi was investigated using the response surface methodology-genetic algorithm mathematical regression model, and the extraction variables were optimized to maximize the flavonoid yield. Furthermore, a simple and efficient ultrafiltration–liquid chromatography–mass spectrometry and molecular docking methods were developed for the rapid screening and identification of acetylcholinesterase inhibitors present in Scutellaria baicalensis Georgi. Subsequently, four major chemical constituents, namely baicalein, norwogonin, wogonin, and oroxylin A, were identified as potent acetylcholinesterase inhibitors. This novel approach, involving the use of ultrafiltration–liquid chromatography–mass spectrometry and molecular docking methods combined with stepwise flow rate counter-current chromatography and semi-preparative high-performance liquid chromatography, could potentially provide a powerful tool for the screening and extraction of acetylcholinesterase inhibitors from complex matrices and be a useful platform for the production of bioactive and nutraceutical ingredients.     

An emerging strategy for tracing the anti-erectile dysfunction components of raw and salt-processed semens of Astragali Complanati by combinatory liquid chromatography–mass spectrometry-based quantitative analysis,efficacy assessment on impotent rats,and partial least squares regression

Semens of Astragali Complanati own anti-erectile dysfunction effect; however, the components which contribute to the anti-erectile dysfunction effect remain unclear. This work raised a strategy that integrates liquid chromatography coupled mass spectrometry-based quantitative analysis, anti-erectile dysfunction assessment on impotent rats, and their relationship analysis for pinpointing anti-erectile dysfunction components from semens of Astragali Complanati. For simultaneous quantification of seven major components in raw and salt-processed semens of Astragali Complanati, an accurate and reliable liquid chromatography–mass spectrometry method was developed under multiple reaction monitoring mode. Of note, chloramphenicol was employed as the internal standard. The method showed good linearity and repeatability, where the recovery rates of each component ranged from 98.1 to 104.7%, and the precisions of intra- and interday were all within 3.4%. The method has been used for quantification of the seven major components in 10 batches of raw and salt-processed semens of Astragali Complanati. Then, the anti-erectile dysfunction effects of raw and salt-processed semens of Astragali Complanati were evaluated on impotent rats. Gray relationship analysis and partial least squares regression were combined for elucidating the relationship. As a result, complanatuside, astragalin, complanatoside B, and kaempferol were found to be responsible for anti-erectile dysfunction effect of Astragali Complanati.