Authentication of cassia seeds on the basis of two-wavelength HPLC fingerprinting with the use of chemometrics

<正>High performance liquid chromatographic(HPLC) fingerprints of Cassia seed,a traditional Chinese medicine(TCM),were developed by means of the chromatograms at two wavelengths of 238 and 282 nm.Then,the two data sets were combined into one matrix.The application of principal component analysis(PCA) for this data matrix showed that the samples were clustered into four groups in accordance with the plant sources and preparation procedures.Furthermore,partial least squares(PLS),back propagation artificial neural network(BP-ANN),and radial basis function artificial neural network(RBF-ANN) were effectively applied to predict the category of the four different samples in the test set.     

Fixation of CO_2 by electrocatalytic reduction to synthesis of dimethyl carbonate in ionic liquid using effective silver-coated nanoporous copper composites

<正>With high surface area,open porosity and high efficiency,a catalyst was prepared and firstly employed in electrocatalytic reduction of CO_2 and electrosynthesis of dimethyl carbonate(DMC).The electrochemical property for electrocatalytic reduction of CO_2 in ionic liquid was studied by cyclic voltammogram(CV).The effects of various reaction variables like temperature,working potential and cathode materials on the electrocatalytic performance were also investigated.80%yield of DMC was obtained under the optimal reaction conditions.     

左旋甲基多巴分子印迹纳米给药系统的合成、表征及药物缓释研究

采用沉淀聚合法合成了左旋甲基多巴(L-Methyldopa, LMD)分子印迹聚合物微球(MIPMs), 并对其合成条件进行了详细研究. 结果表明, 聚合温度和引发剂的用量对微球的大小和形态有较大的影响, 微球的粒径随聚合温度的降低而增大, 随偶氮二异丁睛(AIBN)量的增大而增大. 而模板分子似乎对微球粒径的影响不是很明显. 通过扫描电镜、静态吸附试验(BET)和斯卡查德分析(Scatchard analysis)、红外光谱分析和模拟人体胃液扩散实验等对微球的外貌形态、吸附性能、分子印迹效果和药物缓释效果进行了表征. BET吸附实验和Scatchard 分析结果表明, 分子印迹聚合微球(MIPMs)的最大静态吸附量是非印迹聚合物微球(NIPMs)的3倍. 药物扩散实验表明, LMD在非印迹微球(NIPMs)上的释药率几乎与时间呈直线关系, 说明其释药过程完全受扩散控制; 而LMD在MIPMs上的释药率则呈曲线上升趋势, 说明其释药过程除了受扩散控制外, 还受到药物模板分子与MIPMs之间的印迹效应的协同作用的控制, 从而达到了缓释药物分子的目的. 实验结果表明, 在模拟胃液中, MIPMs释放药物的持续时间(10 h)是NIPMs持续时间(5 h)的2倍, 表明分子印迹微微球确实具有缓释药物的效果. 因此, MIPMs有望进一步应用于LMD药物缓释系统的研究.     

Determination of total and non-water soluble iodine in atmospheric aerosols by thermal extraction and spectrometric detection (TESI)

Iodine has recently been of interest in atmospheric chemistry due to its role in tropospheric ozone depletion, modification of the HO/HO₂ ratio and aerosol nucleation. Gas-phase iodine chemistry is tightly coupled to the aerosol phase through heterogeneous reactions, which are dependent on iodine concentrations and speciation in the aerosol. To date, the only method available for total iodine determination in aerosols is collection on filters by impaction and quantification by neutron activation analysis (NAA). NAA is not widely available to all working groups and is costly to commission. Here, we present a method to determine total iodine concentrations in aerosol impact filter samples by combustion of filter sub-samples (∼5 cm²) at 1,000 °C, trapping in deionised water and quantification by UV/Vis spectroscopy. Both quartz and cellulose filters were analysed from four separate sampling campaigns. The method proved to be sensitive (3σ = 6 ng absolute iodine ≈ 3 pmol m⁻³) precise (RSD ∼ 5%) and accurate, as determined by external and standard addition calibrations. Total iodine concentrations ranged from 10 pmol m⁻³ over the Southern Ocean to 100 pmol m⁻³ over the tropical Atlantic, in agreement with previous estimates. The soluble iodine concentration (extracted with water and measured by ICP-MS) was then subtracted from the total iodine to yield non-water-soluble iodine (NSI). The NSI fraction ranged from 20% to 53% of total iodine, and thus can be significant in some cases.     

苯甲撑肼基二硫代甲酸甲酯热裂解的机理研究

采用密度泛函理论对苯甲撑肼基二硫代甲酸甲酯的热裂解反应机理进行了研究. 计算结果表明, 烯胺碳上氢的六元环迁移途径比硫酰胺氢的四元环迁移途径更容易发生. 同时, 从机理上解释了苯环上的取代基电子效应对该类化合物裂解的影响, 即吸电子基抑制裂解反应的发生, 而推电子基则产生相反的效果.     

Analytical magnetapheresis of magnetically susceptible particles

Analytical magnetapheresis is a newly developed technique for analyzing magnetic particles. The magnetically susceptible particles form deposition patterns after flowing through a separation channel in a magnetic field. The separation channel requirements for analytical magnetapheresis are an excellent seal for the carrier flow and ease of disassembly after magnetapheresis. Previously used separation channels often exhibit variable channel leakage and unstable flow velocities. We improved the separation channel assembly to ensure stable, high flow velocities and characterized the system with various magnetically susceptible and labeled particles. Our new separation channel featured silicone sealant with embedded nylon wires and met analytical magnetapheresis requirements. Characterization of this system was performed using several magnetically susceptible particles, and we studied a variety of diamagnetic sample labels with paramagnetic ions and magnetically susceptible particles at different flow-rates and solution pH values. The minimal labeling concentration for complete deposition was determined to be approximately 2.50 x 10(10) ions per particle for test samples at a flow velocity of 0.67 mm s(-1) and a magnetic field gradient of 2.8 T mm(-1). Silicas, yeasts and blood cells were used for these studies. We determined that the minimal difference in magnetic susceptibility (delta(chi)) for successful separation was approximately 2.00 x 10(-6) [SI]. The magnetic susceptibilities of Dynabeads M-450 at several separation distances and flow-rates were determined to be 0.25 [SI], within 2% of values published by other workers. The magnetic susceptibilities of various ion-labeled yeasts and cells were determined and most varied by less than 5% at different flow-rates. The results of this study provide very important references for analytical magnetapheresis applications.     

内型2—（3,3—二甲基—2—降冰片基）丁醛及其衍生物的合成

以内型３，３－二甲基－２－降冰片基乙醛（１）与叔丁胺反应制得醛亚胺（２），依次和溴化乙基镁，碘乙烷反应制得内型２－（３，３－二甲基－２－降冰片基）丁醛的亚胺（４），再经水解得内型２－（３，３－二甲基－２－降冰片基）丁醛（５）。后者经与乙二醇缩醛化及氧化分别制得该醛的缩醛（６）及羧酸（７）。这些化合物均为新化合物，经纯化后进行了结构分析，并对其质谱进行了讨论。     

酶-配体复合物亲和性的计算

描述了一种新的计算酶－配体复合物亲和性的方法．它考虑了酶－配体结合过程中自由能变化的各主要因素，并利用经验公式加以计算、从蛋白质结构数据库中选取了66个酶－配体复合物作为训练集，利用回归分析得出最后的模型．此模型通用于各种类型的酶－配体复合物，计算结果比技准确，预测算合物解离常数的平均偏差小于一个数量级．此方法还可以定量评价配体分子中每个部分对结合过程的贡献大小，可以为先导他合物的优化提供非常直接的信息     

Insertion reactions of phenyl isocyanate into hafnium nitrogen bonds: synthesis and reactivity of hafnium complexes bearing substituted pyrrolyl ligands

A bis(diethylamido)hafnium compound [C₄H₃N(CH₂NMe₂)-2]₂Hf(NEt₂)₂ (1) has been prepared in 79% yield by reacting Hf(NEt₂)₄ with 2 equiv. of [C₄H₃NH(CH₂NMe₂)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt₂ bonds to generate [C₄H₃N(CH₂NMe₂)-2]₂Hf[PhNC(NEt₂)O]₂ (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C₄H₃N(CH₂NMe₂)-2]Hf[PhNC(NEt₂)O]₃ (3). For comparison, reacting Hf(NEt₂)₄ with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt₂)O]₄ (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt₂ bonds, which are all partially doubly bonded.     

原位反应合成Mo-Si化合物系复合材料

采用反应烧结法原位合成了Mo Si系化合物复合材料，利用X射线衍射仪、扫描电镜和电子探针等考察了材料的显微结构和相组成.结果表明，随原料粉中Mo含量的增加， Mo Si系反应生成物依次向MoSi2→Mo5Si3→Mo3Si变化；各相分布较为均匀，组织致密，晶粒细小.