Direct electrochemical detection of glucose in human plasma on capillary electrophoresis microchips

We developed an electrochemical detector on a hybrid chip for the determination of glucose in human plasma. The microchip system described in this paper consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate. The copper microelectrode is fabricated by selective electroless deposition. The fabrication of the decoupler is performed by platinum electrochemical deposition on the metal film formed by electroless deposition. Factors influencing the performance, including detection potential, separation field strength, and buffer concentration, were studied. The electrodes exhibited good stability and durability in the analytical procedures. Under optimized detection conditions, glucose responded linearly from 10 microM to 1 mM. Finally, glucose in human plasma from three healthy individuals and two diabetics was successfully determined, giving a good prospect for a new clinical diagnostic instrument.     

Simultaneous determination of noradrenaline and dopamine in Portulaca oleracea L. by capillary zone electrophoresis

A simple and rapid capillary electrophoretic method was developed for the simultaneous determination of noradrenaline (NA) and dopamine (DA) in Portulaca oleracea L. The buffer solution used in this method was 40 mM tris (hydroxymethyl) aminomethane (Tris)-H3PO4 at pH 2.00 containing 15% methanol. The effects of pH value, organic modifier, and applied voltage were investigated. The linear ranges of NA and DA were 0.5-100 microg/mL (r=0.9952) and 6.25-200 microg/mL (r=0.9992), respectively. The relative standard deviations of the corrected peak area were 6.73% and 4.26%, respectively. NA and DA in Portulaca oleracea L. were simultaneous determined successfully within 5.6 min. In this way, the contents of NA and DA in different parts (stem, leaves, and seeds) of P. oleracea L. and in different extracts of leaves with different solvents (distilled water, 50% methanol, and methanol) were studied.     

Total synthesis of the ramoplanin A2 and ramoplanose aglycon

A convergent total synthesis of the ramoplanin A2 and ramoplanose aglycon is disclosed. Three key subunits composed of residues 3-9 (heptapeptide 15), pentadepsipeptide 26, and pentapeptide 34 (residues 10-14) were prepared, sequentially coupled, and cyclized to provide the 49-membered depsipeptide core of the aglycon. Key to the preparation of the pentadepsipeptide 26 incorporating the backbone ester was the asymmetric synthesis of an orthogonally protected L-threo-beta-hydroxyasparagine and the development of effective and near-racemization free conditions for esterification of its hindered alcohol (EDCI, DMAP, 0 degrees C). The coupling sites were chosen to maximize the convergency of the synthesis including that of the three subunits, to prevent late stage racemization of carboxylate-activated phenylglycine-derived residues, and to enlist beta-sheet preorganization of an acyclic macrocyclization substrate for 49-membered ring closure. As such, macrocyclization at the chosen Phe(9)-D-Orn(10) site may benefit from both beta-sheet preorganization as well as closure at a D-amine terminus. Deliberate late stage incorporation of the subunit bearing the labile depsipeptide ester and a final stage Asn(1) side chain introduction provides future access to analogues of the aglycons which themselves are reported to be equally potent or more potent than the natural products in antimicrobial assays.     

四溴代邻苯二甲酸根桥联的双核钴（Ⅱ）配合物的合成和表征

合成和表征了４种以四溴代邻苯二甲酸根阴离子（４Ｂｒ－ＰＨＴＨ）桥联、以１，１０－菲咯啉（ｐｈｅｎ），５－硝基－１，１０－菲咯啉（ＮＯ_２－ｐｈｅｎ），２，２′－联吡啶（ｂｐｙ）和４，４′－二甲基－２，２′－联吡啶（Ｍｅ_２ｂｐｙ）端接的双核钴（Ⅱ）配合物［Ｃｏ_２（４Ｂｒ－ＰＨＴＨ）（Ｌ）_４］（ＣｌＯ_４）（Ｌ＝ｐｈｅｎ（ｌ），ＮＯ_２－ｐｈｅｎ（２），ｂｐｙ（３），Ｍｅ_２ｂｐｙ（４））。基于ＩＲ光谱、元素分析、电导测量等方法推定配合物具有四溴代邻苯二甲酸根桥联结构和Ｃｏ（Ⅱ）离子具有畸变的八面体配位环境。进行了配合物变温磁化率（７５～３００Ｋ）的测定，其数据已用从自旋哈密顿符导出的磁方程拟合，求得交换参数Ｊ＝－０．８７ｃｍ~（－１）（１），－０．８４ｃｍ~（－１）（２），－０．８２ｃｍ~（－１）（３），－０．８５ｃｍ~（－１）（４），表明金属离子间有弱的反铁磁性自旋交换相互作用。     

双电层相互重叠时蒙脱胶体表面阴离子的负吸附

本文用Ag-AgCl电极判断平衡,测定双电层处于不同重叠程度下肢体表面阴离子的负吸附量Γ.结果表明,胶体表面双电层相互重叠程度可由两胶体表面间的中点电位φd与外Helmhotz面处的电位φd之比表征;阴离子负吸附随双电层重叠程度和电解质浓度的增加而显著减小.     

Vinyl-polymerization of norbornene with novel anilido–imino nickel complexes/methylaluminoxane: Abnormal influence of polymerization temperature on molecular weight of polynorbornenes

Herein reported are investigations of norbornene polymerization by novel anilido–imino nickel complexes [(Ar¹NCHC₆H₄NAr²)NiBr]₂ (Ar¹ = Ar² = 2,6-dimethylphenyl, 1; Ar¹ = 2,6-dimethylphenyl, Ar² = 2,6-diisopropylphenyl, 2; Ar¹ = Ar² = 2,6-diisopropylphenyl, 3; Ar¹ = 2,6-diisopropylphenyl, Ar² = 2,6-dimethylphenyl, 4) activated with methylaluminoxane (MAO). It was found that at polymerization temperatures below 50 °C, the average molecular weights of the obtained polynorbornenes catalyzed by these four catalytic systems increase with raising temperature, displaying bimodal distribution in GPC curves. The abnormal influence of polymerization temperature could be attributed to the existence of two kinds of catalytic species: heterobimetallic species LNi(II)(μ-Me)₂AlMe₂ (I) and monometallic species LNi(II)Me (II) (L = anilido–imino ligand) at lower temperature. The former affords a lower molecular weight polymer and the latter higher molecular weight one. With raising polymerization temperature above 50 °C, the species I disappears and only species II exists in polymerization systems, resulting in a normal relation of molecular weight to polymerization temperature. From a kinetic study of the norbornene polymerization catalyzed by 1/MAO catalyst at 70 °C, the polymerization rate (R_p) can be expressed by the formulation: R_p = k[NBE]^1.93[Ni]^0.88. Moreover, the mechanism of the norbornene polymerization using the anilido–imino nickel complexes activated with MAO is also presented and discussed.     

Effect of amphiphilic molecules upon chromatic transitions of polydiacetylene vesicles in aqueous solutions

Effect of amphiphilic molecules upon the chromatic transitions of polymerized 10,12-pentacosadiynoic acid (PCDA) vesicles in aqueous solutions was reported. The colorimetric response of polymerized PCDA vesicles for 1-pentanol is higher than that for ethanol due to more hydrophobic property of 1-pentanol. The colorimetric response of polymerized PCDA vesicles for sodium dodecyl sulfate (SDS) and Triton X-100 is lower than that for cetyltrimethylammonium bromide (CTAB). The strong ability of CTAB to induce chromatic transition of the vesicles is related to the positively charged headgroups of CTAB, which favors approach of CTAB to the negatively charged carboxylate groups at the vesicle surface. The insertion of alkyl chain of CTAB into the hydrophobic domain perturbs the conformation of the conjugated polymer backbone and induces color change of polydiacetylene vesicles. For a series of alkylamine hydrochloric salts, the longer the alkyl chain, the stronger the ability of alkylamine to induce chromatic transition of polydiacetylene vesicles.     

表面修饰二氧化锡纳米微晶的制备与表征

制备了硅烷偶联剂KH-570表面修饰的SnO2纳米微晶，通过FT-IR、XPS、TEM和TG-DTA对其结构和表面特性进行表征和研究. FT-IR和XPS分析结果确证了KH-570与SnO2表面是以化学键合或物理吸附方式相结合,粒子表面存在酯基等有机官能团的红外吸收特征；观测到KH-570中Si原子的Si2s和Si2p谱线. TEM分析表明，表面修饰反应增强了SnO2纳米微晶的疏水性和分散性.由XPS和TG的实测数据探讨了纳米粒子具有较低包覆量的可能原因.     

An <Emphasis Type="BoldItalic">in silico</Emphasis> approach for screening flavonoids as P-glycoprotein inhibitors based on a Bayesian-regularized neural network

Summary P-glycoprotein (P-gp), an ATP-binding cassette (ABC) transporter, functions as a biological barrier by extruding cytotoxic agents out of cells, resulting in an obstacle in chemotherapeutic treatment of cancer. In order to aid in the development of potential P-gp inhibitors, we constructed a quantitative structure–activity relationship (QSAR) model of flavonoids as P-gp inhibitors based on Bayesian-regularized neural network (BRNN). A dataset of 57 flavonoids collected from a literature binding to the C-terminal nucleotide-binding domain of mouse P-gp was compiled. The predictive ability of the model was assessed using a test set that was independent of the training set, which showed a standard error of prediction of 0.146 ± 0.006 (data scaled from 0 to 1). Meanwhile, two other mathematical tools, back-propagation neural network (BPNN) and partial least squares (PLS) were also attempted to build QSAR models. The BRNN provided slightly better results for the test set compared to BPNN, but the difference was not significant according to F-statistic at p = 0.05. The PLS failed to build a reliable model in the present study. Our study indicates that the BRNN-based in silico model has good potential in facilitating the prediction of P-gp flavonoid inhibitors and might be applied in further drug design.     

Elutionseigenschaften des Ethylendiamins zur ionen-chromatographie von metallionen

(Elution characteristics of ethylenediamine in ion-chromatography of metal ions). Studies are reported on the action of ethylenediamine with citric or oxalic acid in the eluent on separations of heavy metals, magnesium and alkaline earth elements on columns of Nucleosil SA-10 and Dionex CS-2. The effect of ethylenediamine on the retention times of the alkaline earth elements and manganese is greater than that of the two organic acids, whereas these organic acids have a greater effect on the retention times of heavy metals. This regularity is useful in separations of the heavy metals and alkaline earth elements.