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991.
Nanoscale Platelet Formation by Monounsaturated and Saturated Sophorolipids under Basic pH Conditions
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Dr. Anne‐Sophie Cuvier Dr. Florence Babonneau Jan Berton Prof. Christian V. Stevens Dr. Giulia C. Fadda Gérard Péhau‐Arnaudet Patrick Le Griel Dr. Sylvain Prévost Dr. Javier Perez Dr. Niki Baccile 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(52):19265-19277
The self‐assembly behavior of the yeast‐derived bolaamphiphile sophorolipid (SL) is generally studied under acidic/neutral pH conditions, at which micellar and fibrillar aggregates are commonly found, according to the (un)saturation of the aliphatic chain: the cis form, which corresponds to the oleic acid form of SL, spontaneously forms micelles, whereas the saturated form, which corresponds to the stearic acid form of SL, preferentially forms chiral fibers. By using small‐angle light and X‐ray scattering (SLS, SAXS) combined with high‐sensitivity transmission electron microscopy imaging under cryogenic conditions (cryo‐TEM), the nature of the self‐assembled structures formed by these two compounds above pH 10, which is the pH at which they are negatively charged due to the presence of a carboxylate group, has been explored. Under these conditions, these compounds self‐assemble into nanoscale platelets, despite the different molecular structures. This work shows that the electrostatic repulsion forces generated by COO? mainly drive the self‐assembly process at basic pH, in contrast with that found at pH below neutrality, at which self‐assembly is driven by van der Waals forces and hydrogen bonding, and thus, is in agreement with previous findings on carbohydrate‐based gemini surfactants. 相似文献
992.
Quantitation of Cu+‐catalyzed Decomposition of S‐Nitrosoglutathione Using Saville and Electrochemical Detection: a Pronounced Effect of Glutathione and Copper Concentrations
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Abdulghani Ismail Sophie Griveau Fanny d'Orlyé Anne Varenne Fethi Bedioui 《Electroanalysis》2015,27(12):2857-2863
S‐nitrosothiols (RSNOs) are composed of nitric oxide (NO) bound to the sulfhydryl group of amino acids of peptides or proteins. There is a great interest for their quantitation in biological fluids as they have a crucial impact on physiological and pathophysiological events. Most analytical methodologies for quantitation of RSNOs are based on their decomposition followed by the detection of the released NO. In order to obtain the optimal sensitivity for each detection method, the total decomposition of RSNOs is highly desired. The decomposition of RSNOs can be obtained by using catalytically active metal ions, such as Cu+, obtained from CuSO4 in presence of a reducing agent such as glutathione (GSH) that is naturally present in biological environment. In this work, we have re‐investigated the decomposition of S‐nitrosoglutathione (GSNO) which is the most abundant in vivo low molecular weight RSNO, with a special emphasis on the effect of CuSO4, GSH, and GSNO concentrations and of their ratio. To this aim, GSNO decomposition optimization was performed by both indirect (Griess assay) and direct (real time electrochemical detection of NO at NO‐microsensor) quantitation methods. Our results show that the ratio between CuSO4, GSH and GSNO should be adjusted to tune the highest decomposition rate of GSNO and the most efficient electrochemical detection of released NO; also it shows the deleterious effect of very high GSH concentration on the detection of GSNO. 相似文献
993.
We study the influence of initial conditions and of friction laws on the propagation of dynamic rupture during the earthquake of 28 June 1992 in Landers, California. We model this earthquake solving the elastodynamic wave equation by a finite difference method and we model observed accelerograms in order to get a better knowledge of the dynamic rupture process of this earthquake. In our model rupture propagates spontaneously under the simultaneous control of the initial stress field and friction. We model friction by a simple slip-weakening law. Finally, we inverted the initial stress field and the friction law from the radiation produced by 1992 Landers earthquake using a trial-and-error method. The dynamic model obtained by trial-and-error inversion provides a very satisfactory fit between synthetics and strong motion data. Rupture history and duration of the Landers earthquake are in good agreement with previous kinematic inversion results, without introducing major changes in final slip distribution on the fault. The solution of the dynamic inverse problem is non-unique because this problem is intrinsically ill-posed. Two complementary mechanical models were inverted in order to model the Landers earthquake, and to reproduce the seismic data. The first model corresponds to the asperity model in which only initial stress distribution is heterogeneous. The second model is a barrier model in which the initial stress was perfectly uniform while rupture resistance was heterogeneous. To cite this article: S. Peyrat et al., C. R. Mecanique 330 (2002) 235–248. 相似文献
994.
995.
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
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.
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
998.
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
999.
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
1000.
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