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551.
552.
Otero C Berrendero MA Cardenas F Alvarez E Elson SW 《Applied biochemistry and biotechnology》2005,120(3):209-223
Fourteen noncommercial preparations of microbial lipases were investigated with respect to their catalytic activity for hydrolysis
and synthesis of ester bonds. Six of the lipases were derived from microorganisms that have not previously been described
as lipase producers, and another four were characterized for the first time. The synthetic reactions were carried out in two
solvents of different polarities (n-heptane and acetone) using a series of fatty acids and primary and secondary alcohols with different chain lengths. Under
the culture conditions employed, Pseudomonas cepacia produced more active enzyme than the other microorganisms. The lipase preparations produced using Ovadendron sulphureo-ochraceum, Monascus mucoroides, Monascus sp., Fusarium oxysporum, Penicillium chrysogenum, Rhodotorula araucariae, Pseudomonas cepacia, Streptomyces halstedii, and Streptomyces sp. were the most efficient catalysts for hydrolysis at lipid-water interfaces. Enzyme preparations from P. cepacia, Streptomyces sp., S. halstedii, and R. araucariae were good biocatalysts for esterification in the polar medium (acetone). When the lipase preparations with the greatest activity
for hydrolytic, reactions were excluded, regression analysis of the data for the hydrolytic and synthetic activities of the
remaining lipase preparations yielded high multiple correllation coefficients for these reactions in both n-heptane and acetone (R=0.82 and 0.91, respectively). 相似文献
553.
Fairfull-Smith née Elson KE Jenkins ID Loughlin WA 《Organic & biomolecular chemistry》2004,2(14):1979-1986
Two novel dehydrating reagents and, based on a phosphonium anhydride and an oxyphosphonium triflate respectively, were prepared by reaction of the corresponding polymer-supported phosphine oxides with triflic anhydride. Reagent, based on the novel phosphorus heterocycle 1,1,3,3-tetraphenyl-2-oxa-1,3-diphospholanium bis(trifluoromethanesulfonate), was found to be a useful reagent for ester and amide formation. A wide range of coupling/dehydration-type reactions, such as ester, amide, anhydride, peptide, ether and nitrile formation, were performed in high yield using the more readily prepared polymer-supported triphenylphosphine ditriflate, which was easily recovered and re-used several times without loss of efficiency. With primary alcohols, both reagents and provide an alternative to the Mitsunobu reaction, where the use of azodicarboxylates and chromatography to remove the phosphine oxide by-product can be avoided. The use of 4-dimethylaminopyridine allowed the esterification of secondary alcohols with to proceed in high yield but with retention of configuration. 相似文献
554.
Alvaro J. Pardey Fernando Hung-Low Gabriela C. Uzcátegui Marisol C. Ortega Clementina Longo 《Reaction Kinetics and Catalysis Letters》2006,88(2):203-208
Summary In this work, a mechanistic study of the hydroxycarbonylation of 1-hexene to heptanoic acid and the water gas shift reaction
(WGSR) catalyzed by the rhodium(I) complexes, [Rh(COD)(amine)2](PF6) (COD = 1,5-cyclooctadiene, amine = 4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) immobilized
on poly(4-vinylpyridine) in contact with water under CO is discussed. Catalytic cycles for these reactions bearing common
Rh-H catalytic species are proposed. 相似文献
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M.O. Orlandi R. Aguiar A.J.C. Lanfredi E. Longo J.A. Varela E.R. Leite 《Applied Physics A: Materials Science & Processing》2005,80(1):23-25
This communication discusses the formation of doped nanobelts produced by a simple route. Tin-doped indium oxide (ITO) nanobelts were obtained by a carbothermal reduction method. The nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and wavelength-dispersive X-ray spectroscopy (WDX). The results show that the nanobelts have a cubic structure, are single crystalline and doped with tin and grow in the [400] direction. PACS 81.07.-b; 61.46.+w; 68.37.Hk; 68.37.Lp 相似文献