排序方式: 共有55条查询结果,搜索用时 15 毫秒
31.
Marie-Louise Filleux-Blanchard Henri Durand Grard Jean Martin 《Magnetic resonance in chemistry : MRC》1970,2(6):539-542
Restricted rotation around the C? C bond in the O?C? C?C? N system is responsible of the s-cis and s-trans conformers as shown by the NMR spectra of vinylogous amides (CH3)2N? CH?CH? CO? R. Substituent effect (nature of R) is discussed in terms of conformational equilibrium. Theoretical line shapes have been computed and fit reasonably well with the experimental spectra; activation functions were also derived. 相似文献
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Bhattacharyya S Salvetat JP Fleurier R Husmann A Cacciaguerra T Saboungi ML 《Chemical communications (Cambridge, England)》2005,(38):4818-4820
Highly crystalline and almost monodisperse spinel cobalt-ferrite nanocrystals are synthesized in a one step process, which has very high coercivity at 10 K and exhibits superparamagnetic behaviour at 300 K. 相似文献
34.
Vincenzo Barone Gabriella Capecchi Yvon Brunel Marie-Louise Dheu Andris Robert Subra 《Journal of computational chemistry》1997,18(14):1720-1728
Parameters suitable for extending the AMBER force field for nucleic acids and proteins to open-shell derivatives of amino acid residues are proposed and tested. Two new atom types (radical carbon [CE] and hydrogen directly bonded to it [HE]) are introduced, whose parameters have been determined by a best fitting of quantum-mechanical computations of the simplest analogue of glycine radical (GlyR) in a peptide. The new force field is able to fit the reference results concerning both the structural parameters and the relative stabilities of the different conformers. It has been next applied to a conformational study of the distortions induced by extraction of the glycine Hα atom in an initially helical structure of a dodecamer of alanine including a central glycine residue. Our results show that the helical structure corresponds to a local energy minimum, but deeper minima are found which correspond to a fully planar GlyR residue included in a distorted helical sequence. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1720–1728, 1997 相似文献
35.
Lauren E. VanGelder Eric Schreiber Marie-Louise Wind Prof. Christian Limberg Prof. Ellen M. Matson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14421-14429
Multimetallic complexes have recently seen increased attention as next-generation charge carriers for nonaqueous redox flow batteries. Herein, we report the electrochemical performance of a molecular iron–molybdenum oxido complex, {[(Me3TACN)Fe][μ-(MoO4κ3O,O′,O“)]}4 (Fe4Mo4O16). In symmetric battery charging schematics, Fe4Mo4O16 facilitates reversible two-electron storage with coulombic efficiencies >99 % over 100 cycles (5 days) with no molecular decomposition and minimal capacity fade. Energy efficiency throughout cycling remained high (∼82 %), as a result of the rapid electron-transfer kinetics observed for each of the complex's four redox events. We also report the synthesis of the analogous synthetic frameworks featuring tungstate vertices or bridging-sulfide moieties, revealing key observations relevant to structure–function relationships and design criteria for these types of heterometallic ensembles. 相似文献
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Plotan M Elliott CT Scippo ML Muller M Antignac JP Malone E Bovee TF Mitchell S Connolly L 《Analytica chimica acta》2011,700(1-2):34-40
The increasing availability and use of sports supplements is of concern as highlighted by a number of studies reporting endocrine disruptor contamination in such products. The health food supplement market, including sport supplements, is growing across the Developed World. Therefore, the need to ensure the quality and safety of sport supplements for the consumer is essential. The development and validation of two reporter gene assays coupled with solid phase sample preparation enabling the detection of estrogenic and androgenic constituents in sport supplements is reported. Both assays were shown to be of high sensitivity with the estrogen and androgen reporter gene assays having an EC(50) of 0.01 ng mL(-1) and 0.16 ng mL(-1) respectively. The developed assays were applied in a survey of 63 sport supplements samples obtained across the Island of Ireland with an additional seven reference samples previously investigated using LC-MS/MS. Androgen and estrogen bio-activity was found in 71% of the investigated samples. Bio-activity profiling was further broken down into agonists, partial agonists and antagonists. Supplements (13) with the strongest estrogenic bio-activity were chosen for further investigation. LC-MS/MS analysis of these samples determined the presence of phytoestrogens in seven of them. Supplements (38) with androgen bio-activity were also selected for further investigation. Androgen agonist bio-activity was detected in 12 supplements, antagonistic bio-activity was detected in 16 and partial antagonistic bio-activity was detected in 10. A further group of supplements (7) did not present androgenic bio-activity when tested alone but enhanced the androgenic agonist bio-activity of dihydrotestosterone when combined. The developed assays offer advantages in detection of known, unknown and low-level mixtures of endocrine disruptors over existing analytical screening techniques. For the detection and identification of constituent hormonally active compounds the combination of biological and physio-chemical techniques is optimal. 相似文献
38.
Aoun B Goldbach A González MA Kohara S Price DL Saboungi ML 《The Journal of chemical physics》2011,134(10):104509
High-energy x-ray diffraction measurements and atomistic molecular dynamics (AMD) numerical simulations have been carried out on 1-alkyl-3-methylimidazolium bromide ionic liquids, C(n)mimBr, with n = 2, 4, and 6. Excellent agreement between experiment and simulation is obtained, including the region of the low-Q peak that has proved problematic in previous work in the literature. In the partial structure analysis of the AMD results, a distinct peak develops at the leading edge of the ring-ring pair distribution function and shifts to lower r with increasing alkyl chain length, indicating that the preferential parallel and antiparallel alignment of neighboring cation rings plays a larger role with increasing chain length. The ring-ring, anion-anion, and ring-anion partial structure factors are dominated by strong charge-ordering peaks around 1.1 A?(-1), corresponding to a distance between neighboring polar entities of D(2) = 5.7 A?. In contrast, the tail-tail S(Q) is dominated by the low-Q peak that rises and moves to lower Q with increasing chain length; the length scale of this structural heterogeneity D(1) increases from about 10 A? in C(2)mimBr to 14.3 A? in C(4)mimBr and 18.8 A? in C(6)mimBr. Both the length scale of the structural heterogeneity and its anomalous temperature dependence in the C(n)mimBr liquids studied here show considerable similarity to results in the literature for C(n)mimPF(6) liquids, indicating a remarkable insensitivity to the form and size of the anion. Our results are consistent with the concept of nanoscale heterogeneity with small, crystal-like moieties. 相似文献
39.
Catherine Brasseur François Brose Alain Pirlot Caroline Douny Gauthier Eppe Guy Maghuin-Rogister Marie-Louise Scippo 《Accreditation and quality assurance》2007,12(10):535-542
High performance liquid chromatography (HPLC) coupled to an ultraviolet (UV), diode array or fluorescence detector (UV/DAD/FLD)
has been used to set up an analytical procedure for the quantification of 16 EU priority polyaromatic hydrocarbons (PAHs)
in smoke flavourings. The following parameters have been determined for the 16 EU priority PAHs: limit of detection, limit
of quantification, precision (repeatability and intermediate precision), recovery and measurement uncertainty, using the concept
of accuracy profiles. They were in close agreement with quality criteria described in the Commission Regulation (EC) no. 627/2006
concerning PAHs in smoke flavourings.
Presented at the AOAC Europe Workshop, November 2006, Limassol, Cyprus 相似文献
40.
M.-L. Scippo P. Willemsen S. Danyi V. Helbo M. Muller J. Martial G. Maghuin-Rogister 《Chromatographia》2004,59(1):S23-S27
The so-called “growth promoters”, steroid hormones and β-agonists, are currently controlled by using hyphenated analytical methods (chromatography coupled to mass spectrometry) or, sometimes for screening purposes, on immunoassays. These methods are often too specific to allow an effective multianalyte control. To develop more efficient assays, the use of hormonal receptors as detection tools (receptor-based binding assays and cell-based assays) is proposed. Receptor-based assays represent useful tools in screening of hormonal residues in food, but they could also be applied in doping control (to detect “new” hormonal substances). Furthermore, these assays could be used to monitor the human exposure to endocrine disruptors. 相似文献