By employing dynamic Monte Carlo simulations, we investigate a coil-to-toroid transition of self-attractive semiflexible polymers and the spatial distributions of nanoparticles in self- attractive semiflexible polymer...By employing dynamic Monte Carlo simulations, we investigate a coil-to-toroid transition of self-attractive semiflexible polymers and the spatial distributions of nanoparticles in self- attractive semiflexible polymer/nanoparticle composites. The conformation of self-attractive semiflexible polymers depends on bending energy and self-attractive interactions between monomers in polymer chains. A three-stage process of toroid formation for self-attractive semiflexible chains is shown： several isolated toroids, a loose toroid structure, and a compact toroid structure. Utilizing the compact toroid conformations of self-attractive semiflexible chains, we can control effectively the spatial distributions of nanoparticles in self-attractive semiflexible polymer nanocomposites, and an unconventional toroid structure of nanoparti- cles is observed.展开更多
文摘By employing dynamic Monte Carlo simulations, we investigate a coil-to-toroid transition of self-attractive semiflexible polymers and the spatial distributions of nanoparticles in self- attractive semiflexible polymer/nanoparticle composites. The conformation of self-attractive semiflexible polymers depends on bending energy and self-attractive interactions between monomers in polymer chains. A three-stage process of toroid formation for self-attractive semiflexible chains is shown： several isolated toroids, a loose toroid structure, and a compact toroid structure. Utilizing the compact toroid conformations of self-attractive semiflexible chains, we can control effectively the spatial distributions of nanoparticles in self-attractive semiflexible polymer nanocomposites, and an unconventional toroid structure of nanoparti- cles is observed.
文摘为寻找新型乙酰羟酸合成酶(EC2.2.1.6,AHAS)抑制剂以克服由靶标突变(P197L突变)所引起的杂草抗性问题,利用"构象柔性度分析"策略设计、合成了一系列烷氧基取代的嘧啶水杨酸衍生物.其中, 9个化合物对P197L突变型AHAS的抗性倍数(RF值)均小于等于1,在酶水平上具有良好的反抗性.特别是2-((4,6-二甲氧基嘧啶-2-基)氧基)-6-(2-氟乙氧基)苯甲酸(5l),被进一步确定为该系列最有效的反抗性AHAS抑制剂(RF=0.31),不仅与氯磺隆(RF=2060)和双草醚(RF=4.57)相比抗性程度大幅降低,并且对野生型At AHAS和P197L突变体的抑制活性均达到了亚微摩尔水平,优于双草醚.此外,在150gai/ha的施用剂量下,2-((4,6-二甲氧基嘧啶-2-基)氧基)-6-(2-(甲氧基)乙氧基)苯甲酸(5a)、2-((4,6-二甲氧基嘧啶-2-基)氧基)-6-(3-(甲氧基)丙氧基)苯甲酸(5f)、2-((4,6-二甲氧基嘧啶-2-基)氧基)-6-(2-氟乙氧基)苯甲酸(5l)和2-((4,6-二甲氧基嘧啶-2-基)氧基)-6-(2,2-二氟乙氧基)苯甲酸(5m)对敏感型和抗性(P197L-AHAS)播娘蒿同时表现出优异的除草活性.值得注意的是,即使在最低剂量37.5 g ai/ha下,化合物5l对这两种杂草的除草防效仍超过85%,表现出良好的活体反抗性,具有深入研究的价值.
