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31.
Pei‐Hong Ni Qi‐Sheng Pan Liu‐Sheng Zha Chang‐Chun Wang Abdelhamid Elaïssari Shou‐Kuan Fu 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):624-631
A novel, near‐monodisperse, well‐defined ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(propylene oxide)‐b‐poly[2‐(dimethylamino)ethyl methacrylate], was synthesized via oxyanion‐initiated polymerization. The initiator was a telechelic‐type potassium alcoholate prepared from poly(propylene glycol) and KH in dry tetrahydrofuran. The copolymers produced were characterized by Fourier transform infrared, 1H NMR, and gel permeation chromatography (GPC). GPC and 1H NMR analyses showed that the products obtained were the desired copolymers, with narrow molecular weight distributions (ca. 1.09–1.11) very close to that of the original poly(propylene glycol). 1H NMR, surface tension measurements, and dynamic light scattering all indicated that the triblock copolymer led to interesting aqueous solution behaviors, including temperature‐induced micellization and very high surface activity. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 624–631, 2002; DOI 10.1002/pola.10144 相似文献
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Wei‐Guang Shan Zai‐Lin Gao You‐Min Ying Jia‐Gui Xiang Fa‐Song Wang Zha‐Jun Zhan 《Helvetica chimica acta》2014,97(11):1526-1530
Two new tirucallane‐type triterpenoids, (24Z)‐tirucalla‐7,24‐diene‐3β,11β,26‐triol ( 1 ) and (3S,24R)‐tirucall‐7‐ene‐3,24,25‐triol ( 2 ), along with the known compound celastrol ( 3 ), were isolated from the root barks of Celastrus stylosus Wall . The structures of 1 – 3 were established by spectroscopic methods, including extensive 2D NMR and MS analyses. It is the first report on tirucallane‐type triterpenoids from the genus Celastrus and may be of vital chemotaxonomic significance. 相似文献
34.
Network polymers in a rubber or a gel often contain non-uniform chain lengths. By means of dynamic Monte Carlo simulations of polymer mixtures with various compositions of two chain lengths, we investigated how the factor of polydispersity influences their strain-induced crystal nucleation. Under a high temperature and a high strain rate, the stretching of both polymers revealed that crystal nucleation is mainly accelerated by the presence of short-chain polymers; nevertheless, both polymers join together in the nucleation process. Further analysis proved that crystal nucleation is initiated from those highly stretched short segments, which are rich on the short-chain polymers. 相似文献
35.
Nan-di Zhou Xiao-lei Gu Xiao-hong Zha Ya-ping Tian 《Applied biochemistry and biotechnology》2014,172(1):351-360
Urethanase produced by Penicillium variabile was purified through ultrasonication, concentration by polyethylene glycol 20,000, and Superdex G-200 gel filtration chromatography. The molecular weight of urethanase was determined to be around 96 kDa by gel filtration. The purified enzyme showed a single band in SDS-PAGE with the molecular weight of ~13.7 kDa, which suggests that the enzyme has a multimeric structure composed of the same subunits. Peptide map fingerprinting analysis was then carried out by MALDI/TOF-TOF MS. Within the known sequences in NCBI, glucosamine-6-phosphate deaminase and 6-phosphogluconate dehydrogenase get high score as compared with urethanase. Sequence analysis informs that N-terminal sequence of urethanase is GTNTADNDAA. The Minchaelis constant (K m) and maximum reaction rate (V m) of urethanase are 27.2 mmol/L and 156.25 μmol/L min, respectively. 相似文献
36.
Highly Diastereo‐ and Enantioselective Michael Addition of Nitroalkanes to 2‐Enoyl‐Pyridine N‐Oxides Catalyzed by Scandium(III)/Copper(II) Complexes 下载免费PDF全文
Lijun Li Sheng Zhang Yanbin Hu Yanan Li Chong Li Prof. Zhenggen Zha Prof. Dr. Zhiyong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):12885-12888
A C2‐symmetric Schiff‐base ligand, derived from tridentate‐Schiff‐base, was developed and successfully applied to the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. With this newly catalytic system, an unprecedented diastereoselectivity was obtained in the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. In addition, a switch in enantioselectivity was achieved by using this newly catalytic system and our previous catalyst. After a facile reduction, the optically active adduct was converted to a biologically active dihydro‐2H‐pyrrol 4 a . Furthermore, a connection of two tridentate‐Schiff‐base subunits proved to be an effective strategy in ligand design. 相似文献
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Qiang-Ming Li Hui Jiang Xue-Qiang Zha Li-Hua Pan Jun Duan 《Natural product research》2020,34(4):563-566
AbstractThe stems of Dendrobium huoshanense have long been used to prevent various diseases, including inflammatory diseases. This study was aimed to explain the anti-inflammatory effect of D. huoshanense stems in LPS-induced RAW 264.7 macrophages and to discover potential anti-inflammatory compounds. Results exhibited that D. huoshanense stems ethanol extract could significantly inhibit LPS-induced production of NO, TNF-α and IL-1β. Based on bioassay guided strategy, four bibenzyls (1–4) were isolated from D. huoshanense stems for the first time. Anti-inflammatory assay showed 1–4 could remarkably inhibit the production of NO in LPS-induced macrophages. Moreover, quantitative RT-PCR analysis displayed that the mRNA levels of iNOs, TNF-α and IL-1β could also be significantly reduced by 1–4. These results suggested that D. huoshanense stems ethanol extract and bibenzyls 1–4 might be well developed as therapeutic agent to prevent inflammatory diseases. 相似文献
39.
Prof. Jen-Shyang Ni Tianliang Min Yaxi Li Menglei Zha Dr. Pengfei Zhang Prof. Chun Loong Ho Prof. Kai Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(25):10265-10271
Planar luminogens have encountered difficulties in overcoming intrinsic aggregation-caused emission quenching by intermolecular π-π stacking interactions. Although excited-state double-bond reorganization (ESDBR) can guide us on designing planar aggregation-induced emission (AIE) luminogens (AIEgens), its mechanism has yet been elucidated. Major challenges in the field include methods to efficiently restrict ESDBR and enhance AIE performance without using bulky substituents (e.g., tetraphenylethylene and triphenylamine). In this study, we rationally developed fluoro-substituent AIEgens with stronger intermolecular H-bonding interaction for restricted molecular motions and increased crystal density, leading to decreased nonradiative decay rate by one order of magnitude. The adjusted ESDBR properties also show a corresponding response to variation in viscosity. Furthermore, their aggregation-induced reactive oxygen species (ROS) generations have been discovered. The application of such planar AIEgen in treating multidrug-resistant bacteria has been demonstrated in a mouse model. The relationship between ROS generation and distinct E/Z-configurational stacking behaviors have been further understood, providing a design principle for synthesizing planar AIEgen-based photosensitizers. 相似文献
40.
纳米荧光粒子YVO_4∶Eu的合成及其在指纹显现中的应用 总被引:1,自引:0,他引:1
以柠檬酸为络合剂,在水相中合成了悬浮稳定性较好的稀土YVO4∶Eu溶胶,采用XRD、TEM、荧光光谱等技术,研究了稀土荧光粒子的尺寸、形貌、晶胞参数及发光性能.结果表明合成的YVO4∶Eu荧光粒子为四方晶系,粒径约为10nm,分散性较好;在pH=9.0时合成的Y0.7VO4∶Eu0.3溶胶具有最大的荧光强度,其最大发射峰在619nm;经乙二胺四乙酸二钠表面修饰后的Y0.7VO4∶Eu0.3纳米荧光粒子能够清晰地显现出光滑客体上的指纹,颜色为红色. 相似文献