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931.
Malika Lahiani-Skiba Aude Coquard Fréderic Bounoure Philippe Vérité Philippe Arnaud Mohamed Skiba 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):197-201
Mebendazole is an antihelmintic drug, active against many intestinal parasites. Its systemic efficacy is limited by its poor
water solubility. The use of natural or derivatized cyclodextrins permeated to multiply notably its apparent solubility, especially
with permethyl β-cyclodextrine (PM β-CD) (multiplied by 4700). The inclusion complex formation between mebendazole and this
methylated β-cyclodextrin, was characterized by mass spectrometry, powder X-ray diffractometry and Fourier transform infrared
spectroscopy: mebendazole seemed to be included in permethyl β-cyclodextrin by its aromatic rings. To prepare inclusion complex
of mebendazole and PMβ-CD by solvent evaporation, acetone may be used and the ratio using lower amount of cyclodextrin (MBZ:CD,
1:2) should be used. 相似文献
932.
Combining deflective dielectrophoretic barriers with controlled pressure driven liquid flows in microfluidic devices allows accurate handling of particles such as biological cells in suspensions. Working towards cell-based lab-on-a-chip applications, a platform permitting rapid testing of devices having different dielectrophoretic and fluidic subunits was developed. The performance of such a system is shown in the cases of (A) flooding a small number of immobilised cells with a dye and (B) transient buffer swapping of a large number of cells in flow. The transition times for moving cells from one reagent to the other are below 0.5 s in the case of flow-through cell dipping. 相似文献
933.
Malvy DJ Guinot C Preziosi P Galan P Chapuy MC Maamer M Arnaud S Meunier PJ Hercberg S Tschachler E 《Photochemistry and photobiology》2000,71(4):466-469
A link between bone mineral density and skin color has been reported recently, and pigmentation has been shown to affect cutaneous vitamin D production. In the present study, we investigated the relationship between phototype, global self-assessed sun exposure, geographical location and vitamin D serum levels in 1191 French adults. When the factors were analyzed separately, individuals with lower phototypes as well as those with lower sun exposure showed significantly lower levels of vitamin D than those with darker phototypes or those with higher sun exposure. However, when factors were analyzed as a whole, the vitamin D status was no longer linked with the phototype, but with sun exposure and geographical location. Since phototypes and global self-assessments of sun exposure were positively linked, our data suggest that lower vitamin D levels in fair-skinned individuals are due to their sun exposure behavior. 相似文献
934.
Abstract— The variation with temperature, pH and light of the ESR signal of hydrated melanin powders from Japanese black hair has been studied. An explanation of the results is proposed on the basis of quinhydrone type complexes and of acid-base equilibria of melanin and its semiquinone radicals. During exposure to light of wavelengths 254–600 nm, both stable and unstable radicals have been observed. The action spectrum for the formation of stable melanin radicals has been determined. 相似文献
935.
The evolution of crystal-structure and chemical-bond characteristics is studied for the series of isotypical compounds TiX2, with X = S, Se, Te. The structure determination of TiTe2 and TiSeTe confirms the existence of an increasing trigonal C3v distortion of metal sites when the chalcogen electronegativity decreases. The ESCA study shows that this distortion is associated with augmentation of the covalent or metallic character of the bonds. The structural and spectroscopic differences appearing from TiS2 to TiSe2 can be interpreted by an orbital delocalization in TiSe2 and TiTe2, which would explain the semimetallic behavior of these compounds. 相似文献
936.
Yannick Gueguen Patrick Chemardin Alain Arnaud 《Applied biochemistry and biotechnology》2001,95(3):151-162
A yeast strain isolated in the laboratory from fruit juices was studied and classified as Candida sake. The strain produces an intracellular beta-glucosidase when grown with cellobiose as the carbon source. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular beta-glucosidase, estimated by gel filtration, was 240 kDa. The tetrameric structure of the beta-glucosidase was determined following treatment of the purified enzyme with sodium dodecyl sulfate. The enzyme exhibited optimum activity at 52 degrees C and pH 4.25 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with the (1-->4)-beta configuration, and from Lineweaver Burk plots, a Km value of 6.9 mmol/L was found for p-nitrophenyl-beta-D-glucopyranoside. The beta-glucosidase was found to be tolerant to glucose inhibition with a Ki value of 0.2 mol/L. 相似文献
937.
Isabelle Fremaux Serge Mazères Andrée Brisson-Lougarre Muriel Arnaud Caroline Ladurantie Didier Fournier 《BMC biochemistry》2002,3(1):21-5
Background
Acetylcholinesterase is irreversibly inhibited by organophosphate and carbamate insecticides allowing its use for residue detection with biosensors. Drosophila acetylcholinesterase is the most sensitive enzyme known and has been improved by in vitro mutagenesis. However, it is not sufficiently stable for extensive utilization. It is a homodimer in which both subunits contain 8 cysteine residues. Six are involved in conserved intramolecular disulfide bridges and one is involved in an interchain disulfide bridge. The 8th cysteine is not conserved and is present at position 290 as a free thiol pointing toward the center of the protein.Results
The free cysteine has been mutated to valine and the resulting protein has been assayed for stability using various denaturing agents: temperature, urea, acetonitrile, freezing, proteases and spontaneous-denaturation at room temperature. It was found that the C290V mutation rendered the protein 1.1 to 2.7 fold more stable depending on the denaturing agent.Conclusion
It seems that stabilization resulting from the cysteine to valine mutation originates from a decrease of thiol-disulfide interchanges and from an increase in the hydrophobicity of the buried side chain. 相似文献938.
Microfluidic systems in proteomics 总被引:7,自引:0,他引:7
Lion N Rohner TC Dayon L Arnaud IL Damoc E Youhnovski N Wu ZY Roussel C Josserand J Jensen H Rossier JS Przybylski M Girault HH 《Electrophoresis》2003,24(21):3533-3562
We present the state-of-the-art in miniaturized sample preparation, immunoassays, one-dimensional and multidimensional analyte separations, and coupling of microdevices with electrospray ionization-mass spectrometry. Hyphenation of these different techniques and their relevance to proteomics will be discussed. In particular, we will show that analytical performances of microfluidic analytical systems are already close to fulfill the requirements for proteomics, and that miniaturization results at the same time in a dramatic increase in analysis throughput. Throughout this review, some examples of analytical operations that cannot be achieved without microfluidics will be emphasized. Finally, conditions for the spreading of microanalytical systems in routine proteomic labs will be discussed. 相似文献
939.
R. Arnaud 《Journal of computational chemistry》1994,15(12):1341-1356
Optimized equilibrium geometries and rotational transition structures for CH3OCH XCH2 (X = H, F, CH3, NH2) and CH3OCF2CH2 radicals are obtained by using unrestructed Hartree-Fock (UHF) and second-order Møller-Plesset perturbation (UMP2) theory; a standard 6-31G* basis set is used for geometry optmizations; single-point energies for all stable rotamers are obtained at the UMP4/6-31 + G*//UMP2/6-31G* level. By analysis of rotamers, it is apparent that an anomeric effect exists for X = F and to a lesser extent for X = NH2. Several isodesmic reactions have been studied for the purpose of obtaining theoretical heats of formation and stabilization energies (SE) of these β substituted radicals and their α isomers; the examination of computed SE shows that in the case of CH3OCHFCH2 and CH3OCF2CH2 radicals, a significant extra stabilization induced by the anomeric effect occurs. The question of nO → σ negative hyperconjugation in β-substituted radicals was explored with the aid of natural bond orbital (NBO) energetic analysis; it appears that nO → σ delocalization plays a predominant role in the conformational preference and stabilization of β fluoro derivatives; on the other hand, the stabilization arising from the oxygen lone pair into the σ orbital does not appear to be the key factor in the conformational preference of the CH3OCHNH2CH2 radical. © 1994 by John Wiley & Sons, Inc. 相似文献
940.
Shiratori Y Magrez A Dornseiffer J Haegel FH Pithan C Waser R 《The journal of physical chemistry. B》2005,109(43):20122-20130
NaNbO(3) powders with various particle sizes (ranging from 30 nm to several microns) and well-controlled stoichiometry were obtained through microemulsion-mediated synthesis. The effect of particle size on the phase transformation of the prepared NaNbO(3) powders was studied using X-ray powder diffraction, Raman spectroscopy, and nuclear site group analysis based on these spectroscopic data. Coarsened particles exhibit an orthorhombic Pbcm (D(2h)(11), no. 57) structure corresponding to the bulk structure, as observed for single crystals or powders prepared by conventional solid-state reaction. The crystal symmetry of submicron powders was refined with the space group Pmc2(1) (C(2v)(2), no. 26). The reduced perovskite cell volumes of these submicron powders were most expanded compared to all the other structures. Fine particles with a diameter of less than 70 nm as measured from SEM observations showed an orthorhombic Pmma (D(2h)(5), no. 51) crystal symmetry. The perovskite formula cell of this structure was pseudocubic and was the most compact one. A possible mechanism of the phase transformation is suggested. 相似文献