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991.
992.
Pirrung MC Liu Y Deng L Halstead DK Li Z May JF Wedel M Austin DA Webster NJ 《Journal of the American Chemical Society》2005,127(13):4609-4624
The principle of methyl scanning is proposed for determination of the sites of interaction between biologically active small molecules and their macromolecular target(s). It involves the systematic preparation of a family of methylated derivatives of a compound and their biological testing. As a functional assay, the method can identify the regions of a molecule that are important (and unimportant) for biological activity against even unknown targets, and thus provides an excellent complement to structural biology. Methyl scanning was applied to demethylasterriquinone B1, a small-molecule mimetic of insulin. A new, optimal total synthesis of this natural product was developed that enables the family of methyl scan derivatives to be concisely prepared for evaluation in a cellular assay. The results of this experiment were used to design a biotin-demethylasterriquinone conjugate for use as an affinity reagent. This compound was prepared in tens of milligram quantities in a four-step synthesis. 相似文献
993.
Zhang J Liu L Ma T Deng X 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(9):1915-1922
Measurements of rotational temperature as low as several hundred Kelvin have been measured using optical emission spectroscopy (OES) in nitrogen direct current (DC) glow discharge. The strongest band of the first negative system of nitrogen was chosen to deduce the rotational temperature at four different positions in nitrogen DC glow discharge, the back of cathode; cathode sheath; positive column; and anode glow. In positive column the rotational temperature increased apparently with the increasing discharge voltage from 500 to 1000 V when the pressure was 10 Pa. But with pressure of 20 Pa the rotational temperature in positive column increased slightly with the increase of discharge voltage. On the contrary, the rotational temperature in cathode sheath took reverse tendencies when the discharge voltage varies from 500 to 1000 V. As regard the anode glow, the rotational temperature at 10 Pa decreased with the increase of discharge voltage, but that at pressure of 20 Pa increased. We attribute the different tendencies of the rotational temperature to the different discharge statues at different pressures. When the discharge voltage varies from 500 to 1100 V, the discharge with pressure of 10 Pa is normal glow and that with 20 Pa is abnormal glow. 相似文献
994.
Bairong Shen Kangnian Fan Wenning Wang Jingfa Deng 《Journal of Molecular Structure》1999,469(1-3):157-161
We present an ab initio study on the adsorption and oxidation of HCHO on the Ag2 dimer. HCHO is found to weakly adsorb on the neutral Ag2 cluster and the adsorption energy increases when the Ag2 cluster is positively charged. The adsorption of HCHO on Ag2 is promoted by pre-adsorbed OH species while coadsorbed H has no effect. The formation of η2-methylendioxy is inhibited if the Ag2 cluster is positively and properly charged, which enhance the selectivity of the partial oxidation of methanol. These results provide insight into the reaction mechanism of HCHO on silver surfaces and may guide the design of novel catalysts. 相似文献
995.
996.
采用热扩散法(TS)和等体积浸渍法制备了MoO3/SiO2催化剂用于草酸二甲酯和苯酚酯交换反应.结果表明,热扩散法制备的10%MoO3/SiO2-TS催化剂较等体积浸渍法制备的10%MoO3/SiO2-C催化剂具有更好的催化性能.运用X射线衍射、Raman光谱、X射线光电子能谱分析、吡啶吸附红外光谱、NH3程序升温脱附等手段对催化剂进行了表征,发现虽然两种方法制备的催化剂都只有弱Lewis酸中心,钼均以氧化钼单体形式存在,未形成解离和聚合,但是10%MoO3/SiO2-TS催化剂较10%MoO3/SiO2-C催化剂表面钼含量更高且MoO3分散得更好.在苯酚用量为0.2mol,10%MoO3/SiO2-TS催化剂用量为1.2g,反应温度为180℃,草酸二甲酯与苯酚的摩尔比为2,反应时间为4h的优化条件下,苯酚转化率可达70.9%,甲基苯基草酸酯和草酸二苯酯的收率分别达63.1%和7.7%. 相似文献
997.
998.
999.
Baoming Ji Dongsheng Deng Zhiqiang Wang Xianming Liu Shaobin Miao 《Structural chemistry》2008,19(4):619-623
Two supramolecular complexes Ni[(Py)2C(OH)2]2·(CH3COO)2·4H2O 1 and Co[(Py)2C(OH)2]2·(CH3COO)2·2H2O 2 have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR spectra, and
X-ray single-crystal diffraction. The X-ray diffraction analysis indicates that the center metal (Ni2+ and Co2+) ions having the same coordination environments are chelated by two pyridyl N atoms and a hydroxyl O atom of the gem-diol ligand in an octahedral geometry. In 1, the lattice water molecules form infinite single helical chains, while in 2, two lattice water molecules are discrete. In their crystal structures, intermolecular O–H···O and C–H···O hydrogen bonds
form an extensive three-dimensional network, which consolidates the crystal packing. 相似文献
1000.
Tianyu Yang Ke-Hu Wang Danfeng Huang Pengfei Li Zhoubin Deng Yinpeng Su Yulai Hu 《Tetrahedron》2019,75(15):2291-2297
An efficient and transition-metal-free method for the synthesis of the structurally diversified pyrroles is described. Various α,β-unsaturated ynones reacted with N-substituted ethyl glycine ethyl ester hydrochlorides in the presence of DBU to form the corresponding products in good yields. This protocol has the advantages of readily available starting materials, mild reaction conditions and a wide scope of substrates, which provides a practical route for the synthesis of polysubstituted pyrroles. 相似文献