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731.
Denis Poncelet Brigitte Poncelet De Smet Ronald J. Neufeld 《Journal of membrane science》1990,50(3):249-267
A simple model of nylon membrane formation was developed for enzyme or biological cell microencapsulation. The model which involves physicochemical effects was shown to be useful for optimizing membrane formation and maintaining high activity of the encapsulated biocatalyst. Simulations were conducted to define the effect of the determinant parameters (pH, solvent, temperature, diamine) on membrane characteristics and formation rate. The membrane thickness was shown to be independent of the microcapsule diameter (25-400 μm) when the pH is controlled during formulation (pH 9.5). At pH levels less than 9.5 and hexanediamine concentrations less than 200 mM, thin membranes resulted and pH values dropped considerably during formulation. The use of an acidic buffer and a diamine with lower dissociation constant and higher solubility in the organic solvent, permitted nylon membrane formation at lower pH levels, potentially resulting in less inactivation of the biocatalyst during immobilization. The membrane thickness was seen to be strongly dependent on the solvent polarity, however the solvent selection is limited by the toxicity to the biocatalyst. Control of temperature was needed for reproducibility of the membrane thickness. 相似文献
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733.
Brigitte S Fox O Petru Balaj Iulia Balteanu Martin K Beyer Vladimir E Bondybey 《Journal of the American Chemical Society》2002,124(2):172-173
Metal ions in unusual oxidation states can be introduced into water clusters using a standard laser vaporization source. Such nanosolutions of a single ion in typically 50 water molecules are comparable to a 1 M bulk solution, and their chemistry can be studied in the ion trap of a Fourier transform ion cyclotron resonance mass spectrometer. We find that a strong acid like hydrogen chloride oxidizes the early transition metal vanadium to the more common +III state, while later first row transition metals retain their unusual +I oxidation state, and the binary metal chlorides M(I)Cl precipitate. 相似文献
734.
735.
Abdelmaoujoud Taia Mohamed Essaber Ali Oubella Abdeljalil Aatif Jacques Bodiguel Brigitte Jamart-Grégoire 《合成通讯》2020,50(13):2052-2065
AbstractWe report the synthesis of new series of heterocyclic systems eugenol 1 derivatives by the mixed condensation reaction of 1,3-dipolar azide and the oxide of p-chlorophenylnitrile on the 4-allyl-2-methoxy-1-(prop-2-yn-1-yloxy)benzene 2. The mono and bicycloadducts, whose structure is homologous to compounds having a broad spectrum of activity, were obtained in good yields. The monocondensation reaction of azides on 4-allyl-2-methoxy-1-(prop-2-yn-1-yloxy)benzene 2 is completely chemoselective, regioselective and stereospecific. The condensation of nitrile oxide on 1,2,3-triazole monocycloadducts prepared was chemoselective and regioselective. The structure of all cycloadducts were characterized and confirmed by the 1H, 13C, 2D nuclear magnetic resonance and mass spectrometry analysis. All the newly synthesized mono and bis-heterocyclic compounds have been selected for their antiproliferative activity against HT-1080 fibrosarcoma, A549 lung carcinoma, and MCF-7 and MDA-MB-231 breast carcinoma cell lines. Among the derivatives, only the compounds 4a, 4b, 5a, 5b, 5d, 5e and 5g showed significant cytotoxicity with IC50 values ranging from 15.31 to 18.81?µM against HT-1080 cells, and 17.32 to 25.94?µM against the other cell lines. 相似文献
736.
737.
738.
Layer-Anions in the Crystal Structures of the Isotypic Compounds Sr2[Ga2S5], Ba2[In2S3], and Ba2[In2Se5] The compounds Sr2[Ga2S5], Ba2[In2S5], and Ba2[In2Se5] have been prepared from stoichiometric mixtures of the elements at temperatures between 1150°C and 1250°C. They are isotypic (space group Pbca, Z = 8) with the lattice constants see ?Inhaltsübersicht”?. In the anionic part of the structure GaS4-(InS4-/InSe4)-tetrahedra share three common vertices to form layers with rings built by four and eight tetrahedra. The cations are placed between the sheets and have the coordination number seven. 相似文献
739.
Thiohydroxamic esters (mixed anhydrides) of aromatic and α,β-unsaturated carboxylic acids undergo clean decarboxylative bromination on treatment with bromotrichloromethane in the presence of a radical initiator. 相似文献
740.
González LJ Castellanos-Serra L Badock V Díaz M Moro A Perea S Santos A Paz-Lago D Otto A Müller EC Kostka S Wittmann-Liebold B Padrón G 《Electrophoresis》2003,24(1-2):237-252
An efficient method for digestion and extraction of proteolytic peptides from silver-stained proteins was applied to the characterization of nuclear proteins from the small cell lung cancer H82 (ATCC HTB 175) cell line previously separated by high-resolution large format two-dimensional gel electrophoresis. From 68 spots, evenly distributed on the gel area and representing a wide range of spot intensities, 63 (92%) were successfully identified by matrix-assisted laser desorption/ionization (MALDI) or electrospray ionozation-mass spectrometry (ESI-MS). In five cases where the identification was not possible, the presence of an intense background apparently due to the leakage of polymers from the microtubes or other plastics, was detected. Extensive analysis of peptide sequences by ESI MS/MS experiments allowed the identification of post-translational modifications, such as acetylation, phosphorylation, deamidation of asparagine residues and the presence of isoaspartic acid. A new protein variant not reported in sequence databases was also detected. 相似文献