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排序方式: 共有410条查询结果,搜索用时 15 毫秒
141.
142.
Alvarado-Caudillo Yolanda Torres José Carlos Bravo Novoa Vanesa Zazueta Jiménez Hortencia Silva Torres-Guzmán J. Carlos Gutiérrez-Corona J. Félix Zazueta-Sandoval Roberto 《Applied biochemistry and biotechnology》2002,98(1-9):243-255
A soluble alcohol oxidase (AO) activity was detected in the mycelium of a filamentous fungus strain named YR-1, isolated from
petroleum-contaminated soils. AO activity from aerobically grown mycelium was detected in growth media containing the hydrocarbons
decane or hexadecane; the enzyme activity exhibited optimum pH for the oxidation of different alcohols (methanol, ethanol,
and hexadecanol) similar to that of the corresponding aldehyde. Zymogram analysis conducted with purified fractions from aerobic
mycelium of YR-1 strain extracts indicated the existence of two AO enzymes (AO-1 and AO-2). Purified samples of both enzymes
analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis indicated the presence of three protein bands with molecular
sizes 20, 38, and 46 kDa that could be part of the native enzyme. In samples of both enzymes, the 46-kDa protein gave a positive
reaction in immunodetection experiments with antibodies directed against AO from Hansenula polymorpha. The purified AO-2 enzyme oxidized different alcohols, although higher activity was displayed with hexadecanol. K
m
values obtained for methanol and hexa-decanol indicated a higher affinity for the latter. Analysis of the aminoter-minal
sequence of the 46-kDa protein of AO-2 enzyme indicated significant similarity to enzymes involved in the metabolism of biphenyl
polychloride compounds. 相似文献
143.
Alloys and intermetallic compounds of Au with the 3d transition metals Fe, Co, and Ni are nonequilibrium phases that have many useful potential applications as catalytic, magnetic, optic, and multifunctional magneto-optic materials. However, the atomically ordered Au-M (M = Fe, Co, Ni) intermetallics are particularly elusive from a synthetic standpoint. Here we report the low-temperature solution synthesis of the L12 (Cu3Au-type) intermetallic compounds Au3Fe, Au3Co, and Au3Ni using n-butyllithium as a reducing agent. Reaction pathway studies for the Au3Co system indicate that Au nucleates first, followed by Co incorporation to form the intermetallic. The nonequilibrium intermetallic nanocrystals have been characterized by powder XRD, TEM, EDS, selected area electron diffraction, and nanobeam electron diffraction, which collectively confirm the compositions and superlattice structures. 相似文献
144.
Pardiñas-Blanco I Hoppe CE Piñeiro-Redondo Y López-Quintela MA Rivas J 《Langmuir : the ACS journal of surfaces and colloids》2008,24(3):983-990
Ribbon-like and branched gold nano- and microstructures were produced by simple heating of diluted aqueous solutions of poly(vinylpyrrolidone) (PVP) and HAuCl4. The reaction was carried out in a one-pot, one-step process at mild temperatures. Modification of the synthesis variables allowed the obtaining of structures with different sizes and branching degrees which formed stable hydrosols with characteristic colors. A mechanism for the growth of the crystals was proposed, based on the aggregation of metal units followed by reorientation and attachment processes facilitated by the presence of low concentrations of the polymer. These anisotropic structures were used to obtain large-area porous coatings on metallic, plastic, and glass substrates and to synthesize homogeneous polymer composites. The resulting gold-modified materials showed an important increase of absorption in the near-infrared (NIR) region of the electromagnetic spectrum, which could find interesting applications in the development of NIR-absorbing filters and coatings. 相似文献
145.
Morales-Serna JA Díaz Y Matheu MI Castillón S 《Organic & biomolecular chemistry》2008,6(20):3831-3836
beta-Galactosyl ceramides have been obtained in excellent yields and stereoselectivities by reacting disarmed glycosyl donors with stannyl ethers. The broad compatibility of stannyl ethers with various leaving group-promoter pairs is demonstrated. 相似文献
146.
The zero-valent iron (ZVI)/H2O2 Fenton system can be considered as an effective solution for the removal of many of the organic pollutants present in the waste waters generated by the drug manufacturing industry. The hydrogen peroxide concentration and dosage rate were studied in order to improve the efficiency of the oxidant in the TOC reduction and, thereby enhance the overall catalytic performance of the ZVI/H2O2 Fenton system. TOC reductions of up to 80 % and BOD5/COD ratios of up to 0.6 were achieved in the waste water as received without dilution (TOCO approximately 5 g L?1) using hydrogen peroxide dose-staggering. This showed that the ZVI/H2O2 process led not only to a decrease in TOC removal but also to an increase in the biodegradability of the by-products formed. The hydrogen peroxide was consumed more efficiently and very low concentrations of iron dissolved (7 mg L?1) were obtained in the final effluents. The final values of COD, BOD5, the suspended solids’ content and the conductivity of the treated waste water met the limits of the Spanish legal industrial discharge, Decree 57/2005 (Ministry of Environment, Local Government and Planning, Community of Madrid, 2005). In addition, the composite thus formed, consisting of zero-valent iron and iron oxide-oxyhydroxides, can be readily removed from the treated effluent, avoiding any post-treatment step. 相似文献
147.
Banfi L Basso A Guanti G Kielland N Repetto C Riva R 《The Journal of organic chemistry》2007,72(6):2151-2160
A short, two-step approach to the synthesis of diazepane or diazocane systems, based on a Ugi multicomponent reaction followed by a subsequent intramolecular SN2 reaction was studied. 1-sulfonyl tetrahydrobenzo[e]-1,4-diazepin-1-ones 1 were obtained in very high yield through a Ugi multicomponent reaction followed by Mitsunobu cyclization. On the other hand, aliphatic 1-sulfonyl 1,4-diazepan-5-ones 2 could be obtained employing different cyclization conditions (sulfuryl diimidazole). A similar approach toward diazocane rings using hydroxamates as nucleophiles was less successful, affording only O-cyclized adducts or unexpected side products. A mechanistic explanation of the observed outcomes is proposed. 相似文献
148.
Remote hydroxylation of methyl groups by regioselective cyclopalladation. Partial synthesis of hyptatic acid-A 总被引:1,自引:0,他引:1
García-Granados A López PE Melguizo E Parra A Simeó Y 《The Journal of organic chemistry》2007,72(9):3500-3509
Hyptatic acid-A (32), a 2alpha,3beta,24-trihydroxyolean-12-en-28-oic acid, previously isolated from Hyptis capitata, was obtained from maslinic acid (2). The regioselective cyclopalladation of the axial methyl group on C-4 of maslinic acid afforded the C-24 hydroxymethylene group due to the presence of a C-2-OR substituent. Nevertheless, hederagenin (7) (23-hydroxy derivative) was formed when this oxygenated group was not present. 相似文献
149.
Background: Pesticide residues are a threat to the health of the global population, not only to farmers, applicators, and other pesticide professionals. Humans are exposed through various routes such as food, skin, and inhalation. This study summarizes the different methods to assess and/or estimate human exposure to pesticide residues of the global population. Methods: A systematic search was carried out on Scopus and web of science databases of studies on human exposure to pesticide residues since 2019. Results: The methods to estimate human health risk can be categorized as direct (determining the exposure through specific biomarkers in human matrices) or indirect (determining the levels in the environment and food and estimating the occurrence). The role that analytical techniques play was analyzed. In both cases, the application of generic solvent extraction and solid-phase extraction (SPE) clean-up, followed by liquid or gas chromatography coupled to mass spectrometry, is decisive. Advances within the analytical techniques have played an unquestionable role. Conclusions: All these studies have contributed to an important advance in the knowledge of analytical techniques for the detection of pesticide levels and the subsequent assessment of nonoccupational human exposure. 相似文献
150.
Dr. Daniel Carbajo Dr. Yolanda Pérez Dr. Jordi Bujons Dr. Ignacio Alfonso 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17355-17359
Dynamic covalent chemistry combines in a single step the screening and synthesis of ligands for biomolecular recognition. In order to do that, a chemical entity is used as template within a dynamic combinatorial library of interconverting species, so that the stronger binders are amplified due to the efficient interaction with the target. Here we employed whole A549 living cells as template in a dynamic mixture of imines, for which amplification reflects the efficient and selective interaction with the corresponding extracellular matrix. The amplified polyamine showed strong interaction with the A549 extracellular matrix in on-cell NMR experiments, while combination of NMR, SPR, and molecular dynamics simulations in model systems provided insights on the molecular recognition event. Notably, our work pioneers the use of whole living cells in dynamic combinatorial chemistry, which paves the way towards the discovery of new bioactive molecules in a more biorelevant environment. 相似文献