异构体

The DFT (B3LYP/6-31 + G) method was used to study the relative stabilities and probable proton transfer in isolated and monohydrated 2,4-dithiothymine molecules in gas phase. The effects of water on relative stabilities and the rate of the proton transfer were analysed. The results indicate that only one tautomer for 2,4-dithiothymine can exist in gas phase.

采用密度泛函方法在B3LYP/6-31+G水平上研究了2，4-二硫基胸腺嘧啶孤立分子和水合物的异构体的相对稳定性和可能的质子迁移反应，分析了水分子的参与对 2，4-二硫基胸腺嘧啶异构体的相对稳定性和质子迁移速率的影响。

Results show that, by using thionyl chloride and N,N-dimethyl formamide as chlorinating reagent and dichloromethane as solvent and taking -15℃ as reaction temperature, Z-iomer crystals with pale white color and stable to temperature can be obtained with an overall yield of 70%.

以2-（2-氨基噻唑－4-基）－2-甲氧亚氨基乙酸为原料，经盐酸化、氯代等反应合成了Z-2-（2-氨基噻唑－4-基）－2-甲氧亚氨基乙酰氯盐酸盐；氯代时以用亚硫酰氯和N，N-二甲基甲酰胺的混合物代替五氯化磷作氯化剂，并考察了温度和溶剂对氯代产物中Z-异构体和E-异构体收率的影响。

Particularly, more promising results were achieved for the separation of dinitrotoluene and trinitrotoluene isomers on these columns than on OV-225 column, which has been proved to be the most suitable column for this purpose.

特别是用于火炸药中DNT、TNT异构体的分析比目前最适合于分析上述异构体的OV-225固定液更为优越，具有较高的应用价值。

The optimal carrier gas velocity of prepared SE-30 series capillary chromatographic columns was studied and used to separate isomeric compounds. The efficiency of SE-30 capillary chromatographic columns has been studied with different diameters, film thicknesses and oven temperatures, using n-do-decane, phenol, aminobenzene, and butyl acetate as test samples.

研究自制的SE-30系列毛细管气相色谱柱的载气最佳线速度，并应用于同分异构体的色谱分离分别用十二烷、苯酚、苯胺、醋酸丁酯作试祥在不同载气线速条件下对不同口径、不同膜厚、不同柱温的SE-30毛细管色谱柱的柱效进行考察，并在最佳线速度条件下分离异戊醇、硝基氯苯、硝基甲苯及二乙苯同分异构体体系。

It may have a preventional function from Alzheimer's disease. Molecular biological studies are shown that apoE isoform has a isoform-specific role to neurodegeneration. ApoE〓 and apoE〓 aid to sustain the stabilization of cytoskeleton protein tau, while apoE〓 hyperphosphorylates tau to destabilize the microtubule protein, which will make neurocyte easy to form neurofibrillary tangles in AD. Clearance of amyloidal peptide by apoE〓 and apoE〓 is more effective than by apoE〓. ApoE〓 has the strongest ability to clear the amyloidal peptide. It is shown that apoE〓 has a stronger prevention from Alzheimer's disease.

分子生物学研究发现，apoE异构体对神经细胞退化表现出异构体特异作用，apoE〓和apoE〓有助于维持微管的稳定性，而apoE〓则使tau蛋白超磷酸化，破坏微管的稳定性，使神经细胞易于形成神经纤维缠结。apoE〓和apoE〓对A β的清除率远远高于apoE〓，apoE〓对A β的清除能力最强，可见apoE〓对AD的发生具有较强的阻止作用。

The separation of optical isomers of 2, 2'-dihydroxy-1, 1'-binaphthyl and 2, 2'-diamino-1, 1'-binaphthyl was studied by reversed-phase high performance liquid chromatography on a chiral stationary phase consisting of-hydroxypropyl-β-cyclodextrin (Cyclobond Ⅰ 2000 SP)using methanol/water as the mobile phase. The effects of mobile phase ratio, flow rate and column temperature on separation of optical isomers of DHBN and DABN were investigated.

在S-羟丙基－β-环糊精手性柱(CyclobondⅠ2000 SP)上用反相高效液相色谱法研究了2，2'-二氨基－1，1'-联萘和2，2'-二羟基－1，1'-联萘光学异构体的分离，考察了流动相组成、流速以及柱温等对联二萘胺和联二萘酚光学异构体分离的影响。

Our calculated results show that the relative stability of the isomers depends on the level of theory used: in the framework of DFT, Au10 trends to form planar structures, while the MP2 calculations show that the three-dimensional isomers are energetically more favorable. Based on the present results, Au10 may be conjecturably a critical species of gold clusters which bridges the planar structures and three-dimensional ones.

计算结果表明Au10团簇异构体的相对稳定性明显依赖所使用的理论方法和泛函，密度泛函结果显示Au10倾向于采用平面结构，且不同的泛函给出异构体的相对稳定性次序也不相同，而MP2计算则显示三维空间结构的Au10团簇更稳定， Au10可能是金团簇从二维结构到三维结构演化的一个临界点。

By means of molecular designing, a series of sodium branched-alkyl benzene sulfonates weresynthesized through seven process, involving Frieded-Crafts reaction, Grignard reaction, sulfonationand neutralization. Those isomers have similar structure, carbons of same quantity, but the position ofalkylaryl dissimilarity. Liner fat acid, metaxylene and halogenated hydrocarbon of different carbonnumber were used as the starting materials. Optimum processing condition was confirmed consideringinfluence of a series of reaction factors such as feed proportioning, quantity of catalysts, quantitysolvent, reaction time, temperature and pressure. Eight kinds of isomers of sodium hexadecylxylolsulfonates were finally synthesized, and characterized by FT-IR.

本文通过分子设计，以不同碳数直链脂肪酸、间二甲苯以及不同碳数的卤代烷为原料，经酰基化、格氏反应、加氢还原、磺化及中和等反应，合成了结构相似、烷烃链碳数一定、芳基在烷烃链不同位置的烷基芳基磺酸盐同分异构体；并考察了原料配比、催化剂用量、反应时间、反应温度、溶剂用量、反应压力等一系列因素对各反应的影响，进而确定最佳工艺条件，最终合成出十六烷基二甲苯磺酸钠的八种同分异构体，利用 FT-IR 对产物结构进行了分析。

The relative stabilities and probable proton transfer in isolated and monohydrated 2-hydroxyimidazole molecules have been studied in gas phase using ab initio (MP2/6-31＋G *) method.

采用从头算方法在MP2/6-31＋G*水平上研究了2-羟基咪唑分子在孤立分子和一水合物的异构体的相对稳定性和可能的质子迁移反应，分析了一个水分子的参与对2-羟基咪唑分子异构体的相对稳定性和质子迁移速率的影响，采用Monte Carlo模拟方法研究了反应体系在水溶液中反应的溶剂化效应。

The aromatic position isomers, such as xylene and nitrotoluene, were separated well. Moreover, some chiral compounds including alcohol, amine, ester etc., were also resolved.

不但对二甲笨、硝甲苯等难分离的芳香族位置异构体，而且对醇、胺、酯等多种类型的手性异构体均有很好的分离能力和手性选择能力。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。