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The title compound △14,15-anhydro-24-thiocarbonylbufalin(1) was prepared by the reaction of natural product bufalin with Lawesson reagent. The crystal structure of 1, C24H30O2S·C24H30O2S, was determined by single-crystal X-ray diffraction analysis. It belongs to monoclinic, space group C2, with a = 30.9845(2), b = 6.8036(3), c = 22.5791(15) , V = 4241.7(4) 3, Mr = 384.21, Z = 4, Dc = 1.204 g/cm3, μ = 1.463 mm-1, F(000) = 1664, S = 1.064, R = 0.0487 and wR = 0.0645 for 4683 unique reflections, of which 3757 were observed(I 2■(I)). The asymmetric unit contains two independent molecules(I and Ⅱ), which are closely similar to each other except for the orientation of the lactone ring. Both conformations of I and Ⅱ are in good agreement with the solution structure in methanol as indicated by 1H-NMR analysis. Due to the presence of heavy atom sulfur in the molecules, the final refinement resulted in a small Flack parameter 0.02(3), permitting the assignments of the absolute configuration. In the solid state, intermolecular hydrogen bonds involving thiocarbonyl group in the lactone moiety and the hydroxyl groups in the steroid moiety ester linked adjacent molecules into a three-dimensional network. Compound 1 showed weak inhibition on Na+/K+-ATPase in contrast to the strong inhibitory activity of the parent compound bufalin, suggesting that the carbonyl group in lactone moiety and the hydroxyl group at C-14 play important roles for the inhibition of Na+/K+-ATPase. 相似文献
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Oral administration of an aceteoside polymer from rose Rosa rugosa (P1-b) and a polysaccharide–peptide complex from abalone mushroom Pleurotus abalonus (LB-1b), both with antioxidant activity, produced antihyperglycaemic effects in alloxan-induced diabetic mice. The expression of insulin, superoxide dismutase and pancreas duodenum homeobox factor-1 essential for pancreatic islet function as estimated by real-time PCR was augmented. The reactive oxygen species-scavenging ability of the rose constituent was notably stronger than the mushroom constituent. Thus, the two biomolecules protected the pancreas from oxidative stress, elevated pancreatic insulin expression and lowered circulating glucose level. 相似文献
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讨论了以中空纤维为载体的碳纳米管/正辛醇固-液协同微萃取机理,建立了中空纤维碳纳米管/正辛醇固-液协同微萃取-高效液相色谱法同时测定复杂样品中微量咖啡酸、阿魏酸和肉桂酸含量的方法.以2.5 cm长的聚偏氟乙烯中空纤维为碳纳米管正辛醇分散液载体,供相为分析物的HCl(pH 2.1)溶液,接受相为pH 12.7的NaOH溶液,在35℃下,搅拌萃取60 min,萃取液进行高效液相色谱紫外检测.在优化的实验条件下,分析物的线性范围均在0.05~50 μg/L,r>0.9990 (n=5);检出限均为0.015μg/L;日内与日间精密度均小于9.8%(n=9),平均回收率为93.8%~115.2%;富集倍数分别为514,942和1084倍.在以中空纤维为支持体的碳纳米管/正辛醇微萃取中,碳纳米管/正辛醇分散液嵌入中空纤维管壁上的微孔中形成了碳纳米管/正辛醇固-液微萃取单元束,对苯丙烯酸类化合物起到协同萃取作用. 相似文献
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提出了一种将新型的神经网络互学习模型和常见的多混沌系统融合互扰的复合流密码方案. 首先利用三个Logistics混沌映射产生的随机序列作为神经网络互学习模型中三个 隐含层神经元的随机输入, 神经网络交互学习达到内部权值同步后, 再将同步权值映射为随机序列并与三个Logistics序列复合产生最终的密钥流. 实验表明, 产生的密钥流具有更好的随机性, 混沌流加密应用效果好.
关键词:
混沌映射
神经网络
权值同步
随机密钥流 相似文献
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用摄动理论研究了一类多频激励下具有非线性弹性力和摩阻力的相对转动非线性动力学模型.探讨了各种组合频率之间的关系,给出了使多种类型共振同时发生的条件,并用重正规化方法得出了模型在各相应条件下解的渐近表达式. 相似文献
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