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排序方式: 共有906条查询结果,搜索用时 15 毫秒
901.
De Bock L Vande Casteele SR Mulliez SM Boussery K Van Bocxlaer JF 《Journal of chromatography. A》2011,1218(6):793-801
For the determination of the in vitro cytochrome P450 activity in microsomes, a quantification method for the probe metabolites, formed during incubation, is required. Due to insufficient sensitivity of a previously developed high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for some of the metabolites, a fast and easy derivatization method with pyridine-3-sulfonyl chloride (PS) is described. Acetaminophen (CYP1A2), dextrorphan (CYP2D6), hydroxy-chlorzoxazone (CYP2E1) and hydroxy-mephenytoin (CYP2C19) can be derivatized because of the presence of a phenolic OH, whereas hydroxy-midazolam (CYP3A4) and hydroxy-tolbutamide (CYP2C9) remain unchanged. As PS improves the ionization efficiency in the positive electrospray ionization (ESI) mode, the sensitivity of the detection is improved significantly and meets requirements for the activity determination. Native negative electrospray type molecules, moreover, become positive ESI candidates. The direct derivatization in the aqueous incubation medium, without any other sample pre-treatment steps, such as evaporation or extraction, makes this procedure easy to perform. The method using 20s microwave irradiation was shown to equal a 10min reaction in a 60°C heating block, consequently simplifying and shortening the process. Collision induced fragmentation of the derivatives resulted in at least one native compound, rather than derivative, specific product ion, thereby improving the selectivity of the method in the multiple reaction monitoring mode. The HPLC-MS/MS method was validated, and was demonstrated to be sensitive, selective, precise and accurate. The absence of a relative matrix effect was established, notwithstanding that an absolute matrix effect was observed. The analysis of a sample after microsomal incubation, from which some of the metabolites could not be quantified using the method without derivatization, proved the usefulness of the method. 相似文献
902.
Yu. N. Panchenko C. W. Bock J. D. Larkin A. V. Abramenkov G. R. De Maré A. M. Banaru 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(12):2156-2164
Scaled quantum mechanical force field (SQM-FF) vibrational analyses of the gauche,Trans,trans,Trans,gauche-conformers of octa-1,3,5,7-tetraene (I) with C
i
and C
2 symmetry at the HF/6-31G//HF/6-31G computational level were used to identify the rotational isomer observed in the IR spectrum
of this excited molecule in the solid state. Geometry optimizations at the MP2(FC)/aug-cc-pVDZ level show that the two non-planar
structures of gTtTg-I have the terminal -CH=CH2 moieties rotated by ∼30.6° with respect to the remainder of the nearly planar skeleton. The MP2 and HF energies of the C
2 conformer are slightly lower than the corresponding values of the C
i
conformer. A set of the experimental wavenumbers relating to the C
2 conformer was determined by the detailed analyses of the experimental IR spectra of compounds obtained by Datta et al. via
photolysis of 1,3,5-cycloterraene and bicycle[4.2,0]octa-2.4-diene. The available experimental wavenumbers correlate better
with the results of our SQM-FF calculations at the HF/6-31G level for the conformer with C
2 symmetry than for the conformer with C
i
symmetry. In further support of these results, the van der Waals molecular volume of the C
2 conformer was calculated to be somewhat smaller than the volume of the C
i
conformer, suggesting that in the solid state, where the close-packing principle comes into play, the C
2 conformer would be preferred. 相似文献
903.
Kelber J Achard MF Garreau-de Bonneval B Bock H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(29):8145-8155
Benzo[ghi]perylene 1,2,4,5,10,11-hexacarboxylic trialkylimide and dialkylimido-dialkyl ester derivatives, displaying a thermodynamically stable hexagonal columnar liquid-crystalline phase at room temperature, have been obtained by the use of previously unexplored chiral racemic α-branched alkylimide functions. One of the trialkylimides described here is the first room temperature columnar solely oligo-alkylimide-substituted arene, and thus constitutes a prototype case of self-assembling organic acceptor materials. As the related hexacarboxylic hexaesters are found to exhibit only a weak tendency to form columnar mesophases, benzo[ghi]perylene 1,2,5,10-tetracarboxylic tetraalkyl esters have been synthesized by regioselective oxidative Diels-Alder addition of maleic anhydride to 3,10-dicyanoperylene, and a room temperature hexagonal columnar mesophase was obtained with branched alkyl chains. The acceptor-type electronic properties of the tri- and diimides have been found to be considerably more pronounced than those of the hexa- and tetracarboxylic esters, and to approach those of the prototype acceptor material C(60). The formation of bathochromically absorbing donor-acceptor complexes was observed with a di- or triimide as acceptor and a tetraester as donor, but not with a hexaester as donor. Exploiting the non-negligible differences in reduction and oxidation potentials between all four types of materials, the minimum HOMO energy difference necessary for charge-transfer-complex formation has been determined to lie between 0.29 and 0.35 eV. 相似文献
904.
Eric Grelet Sébastien Dardel Harald Bock Michel Goldmann Emmanuelle Lacaze Frédéric Nallet 《The European physical journal. E, Soft matter》2010,31(4):343-349
The structure and the orientation of thermotropic hexagonal columnar liquid crystals are studied by grazing incidence X-ray
diffraction (GIXD) for different discotic compounds in the geometry of open supported thin films. Whatever the film deposition
mode (either spin-coating or vacuum evaporation) and the film thickness, a degenerate planar alignment with the liquid crystalline
columns parallel to the substrate is found. However, if a specific thermal process is applied to the liquid crystal film,
homeotropic anchoring (columns normal to the interface) can be stabilized in a metastable state. 相似文献
905.
Spectral characteristics and amplitude tunability of a long period grating with a dual- resonance inside fiber loop mirror are studied in terms of applied stress caused by elongation. Inserting the polarization controller between grating and part of polarization maintaining fiber in the loop structure enables tuning of resonance and interferometric peaks. The maximum sensitivity of demonstrated sensor is of 1.943?dB/mε for the range of 1.1–4.4 mε. Combination of these two optical components allows to measure strain in a wider range comparing with sensors based on standard long period grating. 相似文献
906.