程序涂渍柱“柱效能程序效应”的研究

本文从理论上给出程序柱“柱效能程序效应”的概念并导出了函数关系式,通过计算机可计算柱效能程序效应与柱内各变量之间的关系,实践证明实验数据的变化趋势与理论数据相符。     

A model for short alpha-neurotoxin bound to nicotinic acetylcholine receptor from Torpedo californica: comparison with long-chain alpha-neurotoxins and alpha-conotoxins

Short-chain alpha-neurotoxins from snakes are highly selective antagonists of the muscle-type nicotinic acetylcholine receptors (nAChR). Although their spatial structures are known and abundant information on topology of binding to nAChR is obtained by labeling and mutagenesis studies, the accurate structure of the complex is not yet known. Here, we present a model for a short alpha-neurotoxin, neurotoxin II from Naja oxiana (NTII), bound to Torpedo californica nAChR. It was built by comparative modeling, docking and molecular dynamics using 1H NMR structure of NTII, cross-linking and mutagenesis data, cryoelectron microscopy structure of Torpedo marmorata nAChR [Unwin, N., 2005. Refined structure of the nicotinic acetylcholine receptor at 4A resolution. J. Mol. Biol. 346, 967-989] and X-ray structures of acetylcholine-binding protein (AChBP) with agonists [Celie, P.H., van Rossum-Fikkert, S.E., van Dijk, W.J., Brejc, K., Smit, A.B., Sixma, T.K., 2004. Nicotine and carbamylcholine binding to nicotinic acetylcholine receptors as studied in AChBP crystal structures. Neuron 41 (6), 907-914] and antagonists: alpha-cobratoxin, a long-chain alpha-neurotoxin [Bourne, Y., Talley, T.T., Hansen, S.B., Taylor, P., Marchot, P., 2005. Crystal structure of Cbtx-AChBP complex reveals essential interactions between snake alpha-neurotoxins and nicotinic receptors. EMBO J. 24 (8), 1512-1522] and alpha-conotoxin [Celie, P.H., Kasheverov, I.E., Mordvintsev, D.Y., Hogg, R.C., van Nierop, P., van Elk, R., van Rossum-Fikkert, S.E., Zhmak, M.N., Bertrand, D., Tsetlin, V., Sixma, T.K., Smit, A.B., 2005. Crystal structure of nicotinic acetylcholine receptor homolog AChBP in complex with an alpha-conotoxin PnIA variant. Nat. Struct. Mol. Biol. 12 (7), 582-588]. In complex with the receptor, NTII was located at about 30 A from the membrane surface, the tip of its loop II plunges into the ligand-binding pocket between the alpha/gamma or alpha/delta nAChR subunits, while the loops I and III contact nAChR by their tips only in a 'surface-touch' manner. The toxin structure undergoes some changes during the final complex formation (for 1.45 rmsd in 15-25 ps according to AMBER'99 molecular dynamics simulation), which correlates with NMR data. The data on the mobility and accessibility of spin- and fluorescence labels in free and bound NTII were used in MD simulations. The binding process is dependent on spontaneous outward movement of the C-loop earlier found in the AChBP complexes with alpha-cobratoxin and alpha-conotoxin. Among common features in binding of short- and long alpha-neurotoxins is the rearrangement of aromatic residues in the binding pocket not observed for alpha-conotoxin binding. Being in general very similar, the binding modes of short- and long alpha-neurotoxins differ in the ways of loop II entry into nAChR.     

Effect of temperature on the mechanism of retention of fullerenes in liquid chromatography using various alkyl bonded stationary phases

Summary The temperature-dependency of the separation of fullerenes in liquid chromatography (LC) has been examined using various alkyl bonded stationary phases. It has been found that a maximum retention temperature exists with long alkyl bonded stationary phases, whereas there is no similar effect with the newly synthesized alkyl bonded phases which have two phenyl groups at the base of the bonded phase. The interpretation of the retention behavior of fullerenes in the low temperature region on alkyl bonded stationary phases is discussed using information obtained by CP-MAS solid-state NMR spectroscopy and LC.     

Analysis of Seven Herbicides by Gas-Liquid Chromatography

Simutaneous analysis of seven commonly used herbicides, 2,4-D methyl ester, 2,4-D methyl ester, 2,4,5-T methyl ester, silvex methyl ester, ramrod, CIPC and DEF, by gas-liquid chromatography with an electron capture detector was attempted. Two packed columns (which are generally used for the analysis of chlorinated pesticides) and two chemically bonded fused silica capillary columns were used for the analysis. When the packed columns were used, ramrod always interfered with the analysis of 2,4-D methyl ester and/or silvex methyl ester. Complete separation with reasonable analysis time can be achieved using one of the chemically bonded fused silica capillary columns.     

Practical capillary gas chromatography—a systematic approach

Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given.     

阳离子交换柱分离-导数光度法测定原油中钒

以 5Br PADAP为显色剂 ,用阳离子交换柱分离干扰离子 ,在波长 6 30nm采用一阶导数光度法测定原油中钒 ,方法灵敏度高 ,摩尔吸光系数为 3.0× 10 5L·mol- 1·cm- 1,较其它光度法测定钒的摩尔吸光系数提高 1～ 2个数量级。对实际样品进行分析并做加标回收试验 ,钒的回收率在97.5 %～ 10 4 .0 %。与ICP AES方法进行对照试验 ,结果相吻合。     

原位合成分子筛膜毛细管色谱柱的研制

吸附型多孔层毛细管柱既耐高温又对气体及烃类异构体有选择性，同时又具有毛细管色谱快速、高效等优点，是解决难分离组分的重要柱型．常用作气一固吸附色谱固定相的有强极性的硅、中极性的氧化铝、非极性的碳质及特殊吸附作用的分子筛．其中分子筛以其独特的吸附作用，在永久性气体和烃类碳数族组成分析中有重要地位．Pruecell和Soulages[1，2]等制备了涂渍型5A和13X型分子筛的毛细管柱，对低碳烃类化合物显示了良好的分离能力，分析柱温较填充柱降低约100℃．邹乃忠等[3～5]也先后制备了分子筛层的毛细管柱用来作直馏汽油的分析．由于通…     

Methane production from synthesis gas using a mixed culture ofR. rubrum M. barkeri,and M. formicicum

The components of synthesis gas, CO, H₂, and CO₂, may be converted into CH₄ biologically through either acetate or H₂/CO₂ as intermediates. Of these two routes, conversion through H₂/CO₂ is preferred. This paper presents results of mixed-culture studies employing the photosynthetic bacteriumR. rubrum for converting CO to CO₂ and H₂ by the water gas shift reaction and two methanogens,M. formicicum andM. barkeri, for converting CO₂ and H₂ into CH₄. Results are presented for triculture operation in two types of reactors, the packed bubble column and the trickle-bed reactor.     

Effect of column diameter on efficiency in capillary supercritical fluid chromatography

Fused silica capillary columns with internal diameters from 100 to 25 μm were coated with SE-54 and evaluated under supercritical fluid chromatographic conditions using carbon dioxide as mobile phase. Experimental results compared well with theoretical predictions. At ten times the optimum mobile phase velocity and for a capacity factor, k of 3, efficiencies of 2300 to 5600 plates m^?1 were obtained for column diameters of 100 to 25 μm, respectively.     

Characterization of plant oils on a monolithic silica column by high-performance liquid chromatography-atmospheric pressure chemical lonization-mass spectrometry

Summary Five plant oils (peanut, pumpkin seed, sesame seed, soybean, and wheat germ) have been analyzed by high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS). Gradient elution was performed with acetone-acetonitrile mobile phases on a short monolithic silica column (SilicaROD, RP-18e, 50 mm×4.6 mm). Identification of plant oil triacylglycerols (TAG) was based on the pseudomolecular ion [M+H]⁺ and the diacylglycerol [M−RCO₂]⁺ fragments. Positional isomers of triacylglycerols were identified from the relative intensities of the [M-RCO₂]⁺ fragments. Principal-component analysis, used to find similarities and differences between the different oils, indicated that the different plant oils could be clearly differentiated according to their triacylglycerol composition. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001