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131.
Sessler JL Maeda H Mizuno T Lynch VM Furuta H 《Chemical communications (Cambridge, England)》2002,(8):862-863
Novel quinoxaline derivatives bearing dipyrromethane or tripyrromethane substituents act as improved anion receptors as compared to the unsubstituted dipyrrolylquinoxaline core from which they are derived. 相似文献
132.
Mohamed Ali Saada Annie Hémon-Ribaud Vincent Maisonneuve 《Journal of fluorine chemistry》2005,126(7):1072-1077
Tren amine cations [(C2H4NH3)3N]3+ and zirconate or tantalate anions adopt a ternary symmetry in two hydrates, [H3tren]2·(ZrF7)2·9H2O and [H3tren]6·(ZrF7)2·(TaOF6)4·3H2O, which crystallise in R32 space group with aH = 8.871 (2) Å, cH = 38.16 (1) Å and aH = 8.758 (2) Å, cH = 30.112 (9) Å, respectively. Similar [H3tren]2·(MX7)2·H2O (M = Zr, Ta; X = F, O) sheets are found in both structures; they are separated by a water layer (Ow(2)-Ow(3)) in [H3tren]2·(ZrF7)2·9H2O. Dehydration of [H3tren]2·(ZrF7)2·9H2O starts at room temperature and ends at 90 °C to give [H3tren]2·(ZrF7)2·H2O. [H3tren]2·(ZrF7)2·H2O layers remain probably unchanged during this dehydration and the existence of one intermediate [H3tren]2·(ZrF7)2·3H2O hydrate is assumed. Ow(1) molecules are tightly hydrogen bonded with -NH3+ groups and decomposition of [H3tren]2·(ZrF7)2·H2O occurs from 210 °C to 500 °C to give successively [H3tren]2·(ZrF6)·(Zr2F12) (285 °C), an intermediate unknown phase (320 °C) and ZrF4. 相似文献
133.
Vincent Remusat Thierry Terme Armand Gellis Pascal Rathelot Patrice Vanelle 《Journal of heterocyclic chemistry》2004,41(2):221-225
A new heterocyclic bioreductive bis‐alkylating agent, 2,3‐bis(chloromethyl)benzo[g]quinoxaline‐5,10‐dione, was prepared in a four‐steps synthesis. It was shown to react under electron transfer conditions with 2‐nitropropane anion by an bis‐SRN1 mechanism to give three C‐alkylation products in excellent yields. Extension of this bis‐SRN1 reaction to various nitronate or malonate anions and S‐centered anions led to a new class of potentially active benzo[g]quinoxaline‐5,10‐dione derivatives. 相似文献
134.
Ning Fang Vincent Chan Kai-Tak Wan Hai-Quan Mao Kam W. Leong 《Colloids and surfaces. B, Biointerfaces》2002,25(4):347-362
High-resolution reflection interference contrast microscopy (HR-RICM) was developed for probing the deformation and adhesion of phospholipid vesicles induced by colloidal forces on solid surfaces. The new technique raised the upper limit of the measured membrane–substrate separation from 1 to 4.5 μm and improved the spatial resolution of the heterogeneous contact zones. It was applied to elucidate the effects of wall thickness, pH and osmotic stress on the non-specific adhesion of giant unilamellar vesicles (ULV) and multilamellar vesicles (MLV) on fused silica substrates. By simultaneous cross-polarization light microscopy and HR-RICM measurements, it was observed that ULV with the wall thickness of a single bilayer would be significantly deformed in its equilibrium state on the substrate as the dimension of its adhesive–cohesive zone was 29% higher than the theoretical value of a rigid sphere with the same diameter. Besides, electrostatic interaction was shown as a significant driving force for vesicle adhesions since the reduction in pH significantly increased the degree of deformation of adhering ULV and heterogeneity of the adhesion discs. The degree of MLV deformation on the solid surfaces was significantly less than that of ULV. When the wall thickness of vesicle increased, the dimension of contact zone was reduced dramatically due to the increase of membrane bending modulus. Most important, the adhesion strength of colloidal adhesion approached that of specific adhesion. Finally, the increase of osmotic stress led to the collapse of adhering vesicles on the non-deformable substrate and raised the area of adhesive contact zone. To interpret these results better, the equilibrium deformation of adhering vesicle was modeled as a truncated sphere and the adhesion energy was calculated with a new theory. 相似文献
135.
Xu Zhao Sarah E. Cleary Ceren Zor Nicole Grobert Holly A. Reeve Kylie A. Vincent 《Chemical science》2021,12(23):8105
Heterogeneous biocatalytic hydrogenation is an attractive strategy for clean, enantioselective C X reduction. This approach relies on enzymes powered by H2-driven NADH recycling. Commercially available carbon-supported metal (metal/C) catalysts are investigated here for direct H2-driven NAD+ reduction. Selected metal/C catalysts are then used for H2 oxidation with electrons transferred via the conductive carbon support material to an adsorbed enzyme for NAD+ reduction. These chemo-bio catalysts show improved activity and selectivity for generating bioactive NADH under ambient reaction conditions compared to metal/C catalysts. The metal/C catalysts and carbon support materials (all activated carbon or carbon black) are characterised to probe which properties potentially influence catalyst activity. The optimised chemo-bio catalysts are then used to supply NADH to an alcohol dehydrogenase for enantioselective (>99% ee) ketone reductions, leading to high cofactor turnover numbers and Pd and NAD+ reductase activities of 441 h−1 and 2347 h−1, respectively. This method demonstrates a new way of combining chemo- and biocatalysis on carbon supports, highlighted here for selective hydrogenation reactions.Heterogeneous chemo-bio catalytic hydrogenation is an attractive strategy for clean, enantioselective C X reduction. 相似文献
136.
137.
Iwan Jerjen Vincent Revol Andreas J. Brunner Philipp Schuetz Christian Kottler Rolf Kaufmann Thomas Luethi Giovanni Nicoletti Claus Urban Urs Sennhauser 《Polymer Testing》2013
The processing of thermoplastics can induce a wide range of defects such as stress whitening, cavitation and porosity, which can adversely affect the reliability of the final products. Hence, fast and effective non-destructive detection methods for such defects are highly important for quality assurance on production lines. In this paper, X-ray dark field imaging is presented as a new non-destructive testing method that allows the visualization of stress whitening or cavitation efficiently. The performance of the method is demonstrated for the case of an injection-moulded polyvinylidene fluoride part that exhibits stress whitening. Whereas the stress whitening could not be detected by conventional X-ray imaging, it was localized by an X-ray dark field image acquired within a few minutes. Once the precise location of the stress whitening was known, it was possible to verify the result by local micro X-ray computed tomography and by a micro section image. 相似文献
138.
139.
Anne-Catherine Huet Monique Bienenmann-Ploum Ursula Vincent Philippe Delahaut 《Analytical and bioanalytical chemistry》2013,405(24):7733-7751
This article presents a review of the current trends in the analysis of coccidiostats in various matrices, focusing principally on screening and rapid methods. Coccidiosis is an infectious disease having a high negative impact on the animal industry. Drugs are therefore necessary to prevent and/or to combat this disease. However, it is also of crucial importance that these veterinary drugs do not enter the human food chain. European legislation has therefore established the boundaries for the use of coccidiosats and has also addressed the unavoidable problem of cross-contamination of the feed, mainly caused by the use of the same production lines. Consequently there is a need for analytical methods and/or analytical strategies for the monitoring and control of the residues of anticoccidials, both in feed and in the resulting matrices for human consumption. In the frame of the European collaborative project CONffIDENCE, such attempts to establish the required analytical tools were made, which required beforehand a review of the state of the art in this domain. Aiming at this objective, in this review we consider the most interesting publications since 2000. In essence, both a rapid approach with mainly immunoassays and chromatographic methods were developed. To date, the obstacle to routine use of the first approach has been its inability to detect more than two compounds simultaneously, but recent developments in flow cytometry have made it possible to detect six coccidiostats at once. On the other hand, an increasingly popular approach for detecting multiple coccidiostats simultaneously is liquid chromatography coupled with tandem mass spectrometry. There remains a need to adapt these analytical methods to legislative requirements. 相似文献
140.
Lanthanide Identity Governs Guest-Induced Dimerization in LnIII[15-MC
N(L-pheHA)-5])3+ Metallacrowns
Prof. Carmelo Sgarlata Bernadette L. Schneider Valeria Zito Dr. Rossella Migliore Prof. Matteo Tegoni Prof. Vincent L. Pecoraro Prof. Giuseppe Arena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17669-17675
Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (LnIII[15-MC N(L-pheHA)-5])3+ metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host-guest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides). 相似文献