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Rapid liquid chromatography-ultraviolet determination of organic acids and phenolic compounds in red wine and must 总被引:1,自引:0,他引:1
A reversed-phase liquid chromatography-ultraviolet (LC-UV) method is proposed for the rapid simultaneous analysis of the main carboxylic acids and polyphenols in must and wine. Good resolution was obtained for citric, tartaric, malic, lactic, acetic, caffeic, ellagic and gallic acids, (-)-epicatechin, quercetin and resveratrol. A novel silica-based column containing ether-linked phenyl groups, with polar end-capping and suitable for low-pH aqueous mobile phases was used and found to be superior to others tested. The method employed a mixture of 0.2% TFA in water and acetonitrile as eluents, showed linearity and precision, and was applied to samples of must and wine. 相似文献
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Lipases in organic solvents catalyse lactonisation or polymerisation of ω-hydroxyesters. Under these conditions the enzymes exhibit both enantioselectivity and prochiral selectivity. This approach was used to develop the synthesis of chiral γ-lactones and A-B type polyesters from racemic or prochiral hydroxyester substrate. 相似文献
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Ruth Birk Ariel Ikan Benami Bravdo Sergei Braun Oded Shoseyov 《Applied biochemistry and biotechnology》1997,66(1):25-30
Production of Β-glucosidase inAspergillus niger Bl is subjected to catabolic repression by glucose.Aspergillus niger Bl grown on bran as a carbon source secreted Β-glucosidase. The maximum level of the enzyme was reached after 7 d of fermentation.
Addition of 1% glucose to the medium suppressed Β-glucosidase production to undetectable levels. In this study, the organic
synthesis of a potential inducer of Β-glucosidase production by A.niger Bl’s reported. Isopropyl-1-thio-Β-D-glucopyranoside (IPTGlc) was synthesized using a two-step organic synthesis protocol.
The H-NMR data agreed with those reported previously for the galactoside analog. When IPTGlc was added 24 h after inoculation
at a final concentration of 0.4 mM, similar levels of Β-glucosidase were reached 3 to 4 d earlier as compared to fermentation
without IPTGlc induction. In practice, this may translate to a more efficient method of producing Β-glucosidase from this
fungus. 相似文献
4.
A. Benami G. Santana B.M. Monroy A. Ortiz J.C. Alonso J. Fandio J. Aguilar-Hernndez G. Contreras-Puente 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):148
The photoluminescence (PL) of silicon nanoclusters embedded in silicon nitride films grown by remote plasma-enhanced chemical vapor deposition at 200 °C, using mixtures of SiCl4/H2/Ar/NH3 is investigated. It was found that the color and the intensity of the PL of the as-grown samples depend on the H2 flow rate, and there is an optimum flow for which a maximum luminescence is obtained. A strong improvement of the PL intensity and change in color was obtained with annealing treatments in the range of 500–1000 °C. The changes in the composition, structure and optical properties of the films, as a function of H2 flow rate and thermal treatments, were studied by means of Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry and ultraviolet–visible transmission measurements. We conclude that the PL can be attributed to quantum confinement effect in silicon nanoclusters embedded in silicon nitride matrix, which is improved when a better passivation of the nanoclusters surface is obtained. 相似文献
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