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31.
Cellulose/antimony(III) oxide composites, Cel/Sb(2)O(3), with oxide loadings of 1.7, 5.4, and 9.2 wt% were prepared by reacting the precursor SbCl(3) reagent with cellulose in dry ethanol solution. The reaction of the Lewis acid and the cellulose fibers occurred at the~amorphous domains of the biopolymer, increasing the crystallinity degree of the composite compared with that of the untreated cellulose. The scanning electron microscopy images and metal mapping for all samples showed that the oxide film layer uniformly covered the fiber surfaces with no detectable agglomerates of the oxide particles. The synchrotron X-ray diffraction patterns indicated that the antimony oxide film was obtained as a crystalline phase with orthorombic structure. The atomic ratios of O/Sb, determined by X-ray photoelectron spectroscopy, indicated that, for Cel/Sb(2)O(3) samples with 9.3 wt% loading, the fiber surface is nearly saturated by the oxide layer. The thermal stability of Cel/Sb(2)O(3) compared to that of untreated cellulose is practically unaffected. Copyright 2000 Academic Press. 相似文献
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33.
The performance of the sorbent polydimethylsiloxane (PDMS) is compared to that of the adsorbents Carbotrap and Tenax for the enrichment of volatile and reactive sulfur compounds. These included: 1- and 2-propanethiol, tetrahydrothiophene, 2-thioethanol and 2-ethylthioethanol. Several artifact-forming reactions were identified on both Tenax and Carbotrap including: H2S elimination and dimerization of thiols. Additionally, permanent adsorption was also observed for heavier solutes. These effects are absent when PDMS is applied. This superior performance is explained by the absence of catalytic or adsorptive activity on PDMS. 相似文献
34.
Sample preparation in analysis of pharmaceuticals 总被引:1,自引:0,他引:1
Dragana Mutavdi Pavlovi Sandra Babi Alka J.M. Horvat Marija Katelan-Macan 《Trends in analytical chemistry : TRAC》2007,26(11):1062-1075
Sample preparation is a very important and essential step in environmental analysis. This article presents an overview of extraction methods for environmental samples, focusing especially on pharmaceuticals as there is great concern about them as pollutants. 相似文献
35.
The CGC analysis of 25 organophosphorus and organonitrogen pesticides was optimized on two different stationary phases, namely a 5% diphenyl dimethyl silicone (SE-54 type) and a 50% diphenyl dimethyl silicone (OV-17 type) by selecting the best temperature program conditions, using computer simulation. 相似文献
36.
Izquierdo S Rúa F Sbai A Parella T Alvarez-Larena A Branchadell V Ortuño RM 《The Journal of organic chemistry》2005,70(20):7963-7971
[Chemical reaction: See text] Several derivatives of (+)- and (-)-2-aminocyclobutane-1-carboxylic acid, 1, have been prepared through enantiodivergent synthetic sequences. The stereoselective synthesis of free amino acid (+)-1 has been achieved, and this product has been fully characterized for the first time. Stereocontrolled alternative synthetic methodologies have been developed for the preparation of bis(cyclobutane) beta-dipeptides in high yields. Among them, enantio and diastereomers have been synthesized. beta,beta- and beta,delta-Dimers resulting from the coupling of a cyclobutane residue and a linear amino acid have also been prepared. The ability of the cyclobutane ring as a structure-promoting unit both in the monomers and in the dimers has been manifested. The NMR structural study and DFT theoretical calculations evidence the formation of strong intramolecular hydrogen bonds giving rise to cis-fused [4.2.0]octane structural units that confer high rigidity on these molecules both in solution and in the gas phase. The contribution of a cis-trans conformational equilibrium derived from the rotation around the carbamate N-C(O) bond has also been observed, the trans form being the major conformer. In the solid state, this equilibrium does not exist, and moreover, intermolecular hydrogen bonds are present. 相似文献
37.
Chemosensors for the marine toxin saxitoxin 总被引:1,自引:0,他引:1
Gawley RE Pinet S Cardona CM Datta PK Ren T Guida WC Nydick J Leblanc RM 《Journal of the American Chemical Society》2002,124(45):13448-13453
Eleven anthracylmethyl crown ethers have been synthesized and evaluated as fluorescence sensors for the marine toxin saxitoxin. Fluorescence enhancement data are consistent with a 1:1 binding complex for all crowns. The binding constants are in the range of 10(4) M(-)(1) in ammonium phosphate buffer (pH 7.1) in 80% ethanol solvent. Selectivity for sensing saxitoxin versus several organic analytes has been demonstrated for the first time. Possible modes of binding are presented, and relevance to saxitoxin monitoring programs are discussed. 相似文献
38.
Applications performed by capillary electrochromatography (CEC) in all its modes, namely packed column CEC (packed-CEC), open tubular CEC (OT-CEC) and pressure-assisted CEC (pseudo-CEC), and published by June 1999 are reviewed. The review is divided into (i) separation of neutral, acidic and basic analytes with the main goal of evaluating column and system performance, (ii) separation according to field of application and/or chemical class, and (iii) separation of chiral analytes. 相似文献
39.
Chambers C Smith F Williams C Marcos S Liu ZH Hayter P Ciaramella G Keighley W Gribbon P Sewing A 《Combinatorial chemistry & high throughput screening》2003,6(4):355-362
The measurement of intracellular calcium fluxes in real time is widely applied within the pharmaceutical industry to measure the activation of G-protein coupled receptors (GPCRhyp;s), either for pharmacological characterisation or to screen for new surrogate ligands. Initially restricted to G(q) coupled GPCRs, the introduction of promiscuous and chimeric G-proteins has further widened the application of these assays. The development of new calcium sensitive dyes and assays has provided sensitive, homogeneous assays which can be readily applied to high throughput screening (HTS). In this paper we describe the full automation of this assay type using a fluorometric imaging plate reader (FLIPR ) integrated into a Beckman/Sagian system to establish a simple robotic system that is well suited for the current medium throughput screening in this area of lead discovery. Using a recently completed HTS we discuss important determinants for FLIPR based screening, highlight some limitations of the current approach, and look at the requirements for future automated systems capable of keeping up with expanding compound files. 相似文献
40.
Lee KJ Mao S Sun C Gao C Blixt O Arrues S Hom LG Kaufmann GF Hoffman TZ Coyle AR Paulson J Felding-Habermann B Janda KD 《Journal of the American Chemical Society》2002,124(42):12439-12446
Overexpression of the cell-surface glycosphingolipid G(M3) is associated with a number of different cancers, including those of the skin, colon, breast, and lung. Antibodies against the G(M3) epitope have potential application as therapeutic agents in the treatment of these cancers. We describe the chemoenzymatic synthesis of two G(M3)-derived reagents and their use in the panning of a phage-displayed human single-chain Fv (scFv) antibody library derived from the blood of cancer patients. Three scFv-phage clones, GM3A6, GM3A8, and GM3A15, were selected for recombinant expression and were characterized using BIAcore and flow cytometry. BIAcore measurements using the purified, soluble scFvs yielded dissociation constants (K(d)) ranging from 4.2 x 10(-7) to 2.1 x 10(-5) M. Flow cytometry was used to evaluate the ability of each scFv to discriminate between normal human cells (human dermal fibroblast, HDFa), melanoma cells (HMV-1, M21, and C-8161), and breast cancer cells (BCM-1, BCM-2, and BMS). GM3A6 displayed cross-reactivity with normal cells, as well as tumor cells, and GM3A15 possessed little or no binding activity toward any of the cell lines tested. However, GM3A8 bound to five of the six tumor cell lines and showed no measurable reactivity against the HDFa cells. Hence, we have demonstrated that a synthetic G(M3) panning reagent can be used to isolate a fully human scFv that is highly specific for native G(M3) on the surface of tumor cells. The result is a significant step toward effective immunotherapies for the treatment of cancer. 相似文献