Asymmetric Pinacol Coupling of Aromatic Aldehydes Catalyzed by TiCl_4(THF)_2-Zn/Chiral Diamines

IntroductionFormationofradicalanionscatalyzedbythetransitionmetalisachallengingfieldinorganicsynthesisasitcanleadtopotentialcontrolofdiastereoselectivityandenan tioselectivityinawiderangeoforganictransformations .1Thereductivecouplingreactionofaldehydesisanimpor tantmethodofcarbon carbonbondformation .Itisalsothemostdirectandefficientmethodofsynthesizingvicinaldi ols .2 ,3VariousmetalssuchasMg ,4 Al,5Zn ,6 Ce ,7Mn ,8Sm ,9Ti,10 Sn11andCr12 havebeenshowntobeefficientinpinacolcoupling .Sincet…     

阻抑动力学光度法测定环境水样中的痕量苯酚

基于在稀硫酸介质中，痕量苯酚能灵敏地阻抑高碘酸氧化苯胺蓝褪色，研究了该阻抑褪色反应的最佳条件及动力学参数，建立了测定痕量苯酚的新方法。该方法的线性范围为0-40.0μg/L，线性回归方程为1g(A1/A2)=0.638c 0.00117，相关系数r=0.9996，检出限为1.2μg/L。该方法简便，灵敏，选择性好，用于环境水样中痕量苯酚的测定，结果准确。     

Degradation of Microcystin-RR by Combination of UV/H2O2 Technique

The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influence factors such as H2O2, pH and UV light intensities were investigated respectively. Degradation of microcystin-RR （MC-RR） could be fitted by either the pseudo-first-order or second-order rate equations. This homogenous system could significantly enhance the degradation rate due to the synergetic effect between UV and H2O2. The degradation mainly followed the mechanism of direct photolysis and .OH oxidation reactions. Experimental results showed that 94.83% of MC-RR was removed under optimal experimental conditions and the UV/H2O2 system provided an alternative to promote the removal of microcystins in drinking water supplies.     

Study on Triplex DNA by Use of Molecular “Light Switch“ Complex of Ru(phen)2(dppx)^2

A new method for the study of triplex DNA is established according the fluorescence enhancement of molecular “Light Switch“ complex of Ru(phen)2(dppx)^2 when it intercalate into triplex DNA.Because the fluorescence intensity of Ru(phen)2(dppx)^2 bonded to triplex DNA is in ths case higher than that bonded to duplex DNA in certain range of DNA concentration,the method is much more sensitive than other methods reported previously.     

针对蛋白质复合物Other类型的打分函数

在不同类型复合物结合界面的物理化学特征不同的基础上, 针对较难预测的Other 类型复合物设计出特异性打分函数, 用于在对接过程中挑选出有效结构. 该函数由原子接触能(EACE)、范德华和静电相互作用能组成,通过多元线性回归方法获得各项的权重系数. 对来自CAPRI benchmark1 中17 个Other 类复合物例子进行打分测试. 结果表明,组合打分能够刻画出Other 类型复合物单体间相互作用的特征, 反映出复合物形成前后的能量变化, 具备一定的从众多样本中筛选出有效结构的能力. 相对于残基成对势(RP), 该组合打分获得了更高的打分成功率. 对CAPRI 第八轮竞赛中两个结构预测模型进行打分排序, 该组合打分也体现出强于RP 的鉴别有效结合模式潜力.     

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate as a solvent for extraction and preconcentration of mercury with determination by cold vapor atomic absorption spectrometry

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C₄tmsim][PF₆] was synthesized and developed as a novel medium for liquid/liquid extraction of inorganic mercury in this work. Under optimal condition, o-carboxyphenyldiazoamino-p-azobenzene abbreviated as CDAA reacted with inorganic mercury to form a neutral Hg-CDAA complex, the complex was rapidly extracted into ionic liquid phase. After back-extracting into aqueous phase with sulfide sodium solution, the mercury concentration was detected by cold vapor atomic absorption spectrometry. The extraction and back-extraction efficiencies were 99.9 and 100.1% for 5.0 μg L⁻¹ standard mercury in 1000 mL of water solution, respectively. The detection limit, calculated using three times the standard error of estimate of the calibration graph, is 0.01 ng of mercury per milliliter water sample. The proposed method has been used to the determination of trace inorganic mercury in natural water with satisfactory results. Moreover, Zeta potential and surface tension of [C₄tmsim][PF₆] solution were measured and applied to explain the extraction mechanism of [C₄tmsim][PF₆] system.     

毛细管气相色谱法测定水体及土壤中溴氟菊酯农药的残留量

建立了新品农药溴氟菊酯在水体及土壤中残留量的测定方法，采用石油醚＋丙酮（３＋１）混合溶剂提取，经浓硫酸＋无水乙醇（１＋１）纯化，用毛细管气相色谱电子捕获检测器测定。该法检出限为０．１×１０－９～２×１０－９，回收率７２．６％～１００．５％，变异系数１．６％～８．５％。     

Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy

We present investigations of the transient photoconductivity and recombination dynamics of quasifree electrons in liquid n-hexane and cyclohexane performed using terahertz time-domain spectroscopy (THz-TDS). Quasifree electrons are generated by two-photon photoionization of the liquid using a femtosecond ultraviolet pulse, and the resulting changes in the complex conductivity are probed by a THz electromagnetic pulse at a variable delay. The detection of time-domain wave forms of the THz electric field permits the direct determination of both the real and the imaginary part of the conductivity of the electrons over a wide frequency range. The change in conductivity can be described by the Drude model, thus yielding the quasifree electron density and scattering time. The electron density is found to decay on a time scale of a few hundred picoseconds, which becomes shorter with increasing excitation density. The dynamics can be described by a model that assumes nongeminate recombination between electrons and positive ions. In addition, a strong dependence of the quasifree electron density on temperature is observed, in agreement with a two-state model in which the electron may exist in either a quasifree or a bound state.     

Sensitive Determination of Cyanide in Cigarette Smoke by Capillary GC with a MicroECD

A sensitive method using capillary gas chromatography coupled with a micro electron capture detector (μECD) has been developed for the determination of cyanide in cigarette smoke. The procedure is based upon the conversion of cyanide to cyanogen chloride by chloramine-T. Cyanogen chloride, dissolved in n-hexane, was analyzed by GC–μECD. Under optimum conditions, the detector response was linear from 25.0 ng mL^?1 to 15.0 μg mL^?1 with relative standard deviation between 0.07 and 3.30%. Recovery ranged from 86.0 to 116.0%. The method was shown to be precise, accurate and linear over the range of concentration of analytes.     

Bandunamide, a Novel Cyclopeptide from the Streptomyces Griseovariabilis bandungensis

A new cyclic octapeptide, bandunamide, was isolated from the acetone extracts of streptomyces griseovariabilis bandungensis. This cyclic octapeptide exhibits strong antimicrobial activity against Phytophthora drechsleri (IC50=15 ng/mL), Colletotrchum higginsiannum(IC50=15.6 ng/mL), Piricularia oxyzae (IC50=0.2 μg/mL), and Fusarium oxysporum f. Sp.(IC50= 100μg/mL). The structure elucidation of bandunamide is herein reported.