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991.
Tingting Fu Janina Oetjen Manuel Chapelle Alexandre Verdu Matthias Szesny Arnaud Chaumot Davide Degli‐Esposti Olivier Geffard Yohann Clment Arnaud Salvador Sophie Ayciriex 《Journal of mass spectrometry : JMS》2020,55(9)
The highly diverse chemical structures of lipids make their analysis directly from biological tissue sections extremely challenging. Here, we report the in situ mapping and identification of lipids in a freshwater crustacean Gammarus fossarum using matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) in combination with an additional separation dimension using ion mobility spectrometry (IMS). The high‐resolution trapped ion mobility spectrometry (TIMS) allowed efficient separation of isobaric/isomeric lipids showing distinct spatial distributions. The structures of the lipids were further characterized by MS/MS analysis. It is demonstrated that MALDI MSI with mobility separation is a powerful tool for distinguishing and localizing isobaric/isomeric lipids. 相似文献
992.
Details of the reaction sequence used for the fluorimetric detection of phosphates by disassembly of transition metal Schiff base complexes were investigated for [FeIII(salen)(H2O)]+, [ZnII(salen)], [MnII(salen)(H2O)2], and [MnIII(salen)(H2O)]+. The reactivity of these compounds towards phosphorus oxoanions of differing charge, number of donor atoms and steric hindrance was detected by UV/Vis and fluorescence spectroscopy in both aprotic organic and aqueous media. Selectivity of [FeIII(salen)(H2O)]+ towards pyrophosphate over all other tested phosphorus-containing analytes was strongly supported. [ZnII(salen)] showed a faster reactivity but was much less selective. In contrast, [MnIII(salen)(H2O)]+ proved to be more stable than the iron complex but generally showed little reactivity towards phosphorus oxoanions. The influence of the charge of the central atom was investigated using the MnII analogue [MnII(salen)(H2O)2]. As expected, the reduced charge resulted in a reactivity comparable to the ZnII complex in organic solution but lead to hydrolysis of the complex in water. Finally, the reaction products of [FeIII(salen)(H2O)]+ with phosphates were characterized by IR spectroscopy and mass spectrometry, providing further insights into the reaction mechanism of the disassembly process. 相似文献
993.
In this paper, two different definitions of the BRST complex are connected. We obtain the BRST complex of topological quantum field theories (leading to equivariant cohomology) from the standard definition of the classical BRST complex (leading to Lie algebra cohomology) provided that we include ghosts for ghosts. Hereby, we use a finite dimensional model with a semi-direct product action ofH DiffM on a configuration spaceM, whereH is a compact Lie group representing the gauge symmetry in this model. 相似文献
994.
Talib M. N. Albayati Sophie E. Wilkinson Arthur A. Garforth Aidan M. Doyle 《Transport in Porous Media》2014,104(2):315-333
Pt-USY-712 (Si/Al = 6) and three SBA-15 catalysts (metal-loaded with 1 wt% Pt, 1 wt% Ni or 0.5 wt% Pt and 0.5 wt% Ni) were prepared and characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD), N \(_{2}\) adsorption porosimetry / BET and transmission electron microscopy (TEM). The catalysts were then tested in the hydroisomerisation and hydrocracking of \(n\) -heptane using a micro-reactor at atmospheric pressure, and the products were analysed by GC-FID. Reaction temperatures ranged from 250– \(400\,\,^{\circ }\hbox {C}\) while the W/F values of \(n\hbox {-C}_{7}\) varied from 224.70–550.57 kg \(\hbox {mol}^{-1}\) . The coke content of each catalyst was measured using thermo gravimetric analysis (TGA). The catalytic activity was highest on Pt-USY-712 at the lowest reaction temperatures due to (a) the presence of strong Brønsted acids sites on the zeolite and (b) the smaller and more highly dispersed metal clusters on Pt-USY-712, relative to Pt-SBA-15. The activity was higher on the bimetallic Pt/Ni-SBA-15 than on mono-metallic Pt-SBA-15 as the co-impregnation of Ni with Pt enhanced the distribution of the metal clusters on the catalyst and resulted in improved surface area for reaction. The Pt-SBA-15 and Pt/Ni-SBA-15 catalysts both had the lowest and approximately equal coke percentages with 0.116 and 0.119 wt%, respectively. 相似文献
995.
Snehangshu Patra Carine Davoisne Stéphanie Bruyère Houssny Bouyanfif Sophie Cassaignon Pierre‐Louis Taberna Frédéric Sauvage 《Particle & Particle Systems Characterization》2013,30(12):1093-1104
The synthesis of highly divided anatase TiO2 nanoparticles displaying 300 m2 g?1 surface area is achieved by following a two‐step synthetic process at room temperature. The particles exhibit a needle‐like morphology composed of self‐assembled 4 nm nanoparticles. The crystallization process from amorphous TiO2.1.6H2O to oriented aggregation of anatase TiO2 proceeds according to a slow solid dehydration process taking place in a large range of pH in deionized water (1 < pH < 12) or alternatively when including a low amount of NH4F(aq) in solution. Driven by their high surface area enhancing the chemical/electrochemical reactivity, it is reported in the case of the anatase TiO2 that a modification in the lithium insertion mechanism is no longer attributable to a two‐phase reaction between the two‐end members LiεTiO2 and Li0.5±αTiO2 when downsizing the particle size, but instead through a complete solid solution all along the composition range. 相似文献
996.
Vanwetswinkel S Heetebrij RJ van Duynhoven J Hollander JG Filippov DV Hajduk PJ Siegal G 《Chemistry & biology》2005,12(2):207-216
We propose a ligand screening method, called TINS (target immobilized NMR screening), which reduces the amount of target required for the fragment-based approach to drug discovery. Binding is detected by comparing 1D NMR spectra of compound mixtures in the presence of a target immobilized on a solid support to a control sample. The method has been validated by the detection of a variety of ligands for protein and nucleic acid targets (K(D) from 60 to 5000 muM). The ligand binding capacity of a protein was undiminished after 2000 different compounds had been applied, indicating the potential to apply the assay for screening typical fragment libraries. TINS can be used in competition mode, allowing rapid characterization of the ligand binding site. TINS may allow screening of targets that are difficult to produce or that are insoluble, such as membrane proteins. 相似文献
997.
Takehiko Yamato Carol Pérez Casas Hideo Yamamoto Mark R. J. Elsegood Sophie H. Dale Carl Redshaw 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):261-269
Regioselective synthesis of bis[(2-pyridylmethyl)oxy]tetrathiacalix[4]arenes was accomplished by a protection–deprotection method using benzyl groups as a protecting group. The conformational studies of distal-bis[(2-pyridylmethyl)oxy]thiacalix[4]arenes in solution and solid state are described. The two-phase solvent extraction data indicated that bis[(2-pyridylmethyl)oxy]tetrathiacalix[4]arenes show strong Ag+ (E%, 97%) affinity. In contrast, no significant E% is observed for K+. A good Job plots proves 1:1 coordination of 1,3-alternate
-3 with Ag+ cation. 1H-NMR Titration of 1,3-alternate-
3 with AgSO3CF3 also clearly demonstrates that a 1:1 complex is formed with retention of the original symmetry. The conformational changes of pyridine moiety from the original outward orientation of the ring nitrogen to the inside orientation toward the thiacalixarene cavity were observed in the process of Ag+ complexation. The down-field shifts of the benzene protons of the benzyl group were also observed and attributed to the conformational deviation from the original face to face overlapping. 相似文献
998.
Aurore Vannier Sophie Duquesne Serge Bourbigot Jenny Alongi Giovanni Camino Ren Delobel 《Thermochimica Acta》2009,495(1-2):155-166
The incorporation of both OMPOSS and Exolit OP950 (zinc phosphinate) into PET leads to increased fire retarding properties and a synergistic effect has been established between the three components. Here the thermal degradation of OMPOSS, Exolit OP950, PET and blends of them is investigated via thermal degradation in pyrolytic and thermo-oxidative conditions. All species formed during the degradation of the additives or the blends are identified by solid state NMR and X-ray diffraction in the condensed phase and by GC–MS in the gas phase. The investigation shows that no chemical interaction occurs between the additives, which suggests that the synergy responsible for the improvement of fire properties of the material has a physical origin. 相似文献
999.
Guy T. Giuffredi Sophie Purser Marcin Sawicki Amber L. Thompson Véronique Gouverneur 《Tetrahedron: Asymmetry》2009,20(6-8):910-920
A highly efficient anti-SE2′ electrophilic fluorination of enantioenriched allylsilanes a subsequent dihydroxylation of the resulting allylic fluorides were used as key steps for the synthesis of three fluorinated carbohydrate analogues, 1,5-di-O-benzyl-2-deoxy-2-fluoro-d-glucitol, 2,6-di-O-benzyl-5-deoxy-5-fluoro-l-glucitol and 1,5-di-O-benzyl-2-deoxy-2-fluoro-d-mannitol. A new catalytic asymmetric route to 1-benzyloxy-4-trimethylsilyl-but-3-yn-2-ol, a common precursor to two advanced allylsilanes, is also described featuring a Noyori asymmetric transfer hydrogenation reaction. 相似文献
1000.
Tamara Elzein Anthony Galliano Sophie Bistac 《Journal of Polymer Science.Polymer Physics》2004,42(12):2348-2353
In this article, we describe an experimental friction study of poly(dimethyl siloxane) (PDMS) networks on metallic substrates such as gold-coated slides, and under different conditions. The friction generates a transfer of a thin layer of PDMS and a preferential orientation of the polymer chains at the interface. However, the characterization of this layer is complicated, given the small amount of matter and the contact with a metallic surface. The polarization-modulation infrared reflexion-absorption spectroscopy (PM-IRRAS), which is an excellent tool for anisotropy and orientation studies, was used to characterize the PDMS transferred layer. Our results showed an induced anisotropy due to the friction, and in which PDMS chains are lying parallel to the gold substrate surface. Our spectroscopic analyzes allowed us to imagine a scheme of PDMS transfer on the gold surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2348–2353, 2004 相似文献