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51.
Hang GONG Nian Fa YANG? Wei Jun TANG Qing Hua FAN Li Wen YANG The College of Chemistry Xiangtan University Xiangtan Laboratory of Chemical Biology Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2005,16(8)
Among the reactions in which C-C bonds are formed, the Baylis-Hillman coupling of aldehydes with α, β-unsaturated carbonylic compounds is currently attracting much interest due to the atom economy, the mild conditions and the generation of functional groups1,2. Furthermore, compared to the Heck, Suzuki and other palladium catalyzed C-C bond forming reaction3, the Baylis-Hillman reaction can be promoted by using organic bases in the complete absence of any metal4. However, almost all the … 相似文献
52.
53.
Mohammad Malakootian Hakimeh Mahdizadeh Abbas Dehdarirad 《Journal of Dispersion Science and Technology》2019,40(6):846-854
Ciprofloxacin is used in the treatment of bacterial infections. Because ciprofloxacin is not effectively degraded by biological processes, advanced oxidation processes such as photocatalytic ozonation are applied to remove this antibiotic from wastewater. The aim of this study was to investigate photocatalytic ozonation for the removal of ciprofloxacin from aquatic environments and optimization of the effective parameters of the process. For this purpose, ZnO nanoparticles were synthesized using the thermal method and immobilized on the surface of stones. The structural properties of the nanoparticles were determined by XRD, TEM, Photoluminescence (PL) and SEM. Experiments were carried out in a Plexiglas reactor supported with the continuous injection of ozone. The effective parameters for removal efficiency were reaction time, initial concentration of ciprofloxacin, pH, photocatalyst concentration and reaction kinetics. The highest ciprofloxacin removal efficiency occurred at the following optimal conditions: pH of 7, reaction time of 30?min, photocatalyst concentration of 3?g/L and initial ciprofloxacin concentration of 10?mg/L. Removal efficiency of 96% was obtained under these conditions. Linear kinetic models showed that the process followed pseudo-first order and Langmuir-Hinshelwood kinetics. This process had a high removal efficiency and suitable for removal of ciprofloxacin from aquatic environments.GRAPHICAL ABSTRACT 相似文献
54.
Nils Siegbahn Mats-Olle Maånsson Klaus Mosbach 《Applied biochemistry and biotechnology》1987,12(2):91-105
A soluble, bifunctional enzyme complex has been prepared by crosslinking lactate dehydrogenase and alcohol dehydrogenase with
glutaraldehyde. The crosslinking was performed on a solid phase while the active sites of alcohol dehydrogenase and lactate
dehydrogenase were held adjacent to one another with the aid of a bis-NAD analog. Subsequently, the enzyme complex was released
from the solid phase. The soluble enzyme complex was then purified by using NAD-Sepharose as an affinity adsorbent. Based
on gel filtration experiments, the complex was estimated to consist of one of each dehydrogenase.
By using a third enzyme, lipoamide dehydrogenase, which competes with lactate dehydrogenase for NADH produced by alcohol dehydrogenase,
the effect of site-to-site orientation was studied. It was found that about 83% of the NADH produced by alcohol dehydrogenase
was oxidized by site-to-site oriented lactate dehydrogenase compared to a figure of only about 61% obtained in an identical
system of separate enzymes. This indicates that given two alternative routes, the preference for the one to lactate dehydrogenase
over the one to lipoamide dehydrogenase is enhanced when lactate dehydrogenase and alcohol dehydrogenase are site-to-site
oriented. 相似文献
55.
Richard C. Woudenberg 《Tetrahedron letters》2005,46(37):6311-6313
A method for selective N-protection of hydroxyalkylbenzimidazoles using 2,2,2-trichloroethylchloroformate (Troc-Cl) applicable to various alkyl chain lengths has been developed. In the specific case of 5-(1-[2,2,2-trichloroethyl formyl]-benzimidazol-2-yl)-propan-1-ol, migration of Troc from the benzimidazole to the primary alcohol occurs in the presence of triethylamine, allowing the choice of selective N-Troc or O-Troc protection. 相似文献
56.
Two amino acid analog resistant mutants of the cyanobacteriumAnabaena sp 287 were isolated after MNNG mutagenesis.Anabaena ST 16, a mutant resistant to the alanine analog D-α-aminobutyric acid andAnabaena ST 25, another mutant resistant to the histidine analog l,2,4-triazole-3-alanine, released alanine and histidine, respectively,
into the medium upon immobilization in alginic acid during diazotrophic growth in fluidized bed reactors. The rates of amino
acid production by the mutants were 4.3 μmol mg chl-1 h-1 of D-alanine byAnabaena ST 16 and 16.6 μnol mg chl-1 h-1 of L-histidine byAnabaena ST 25. Nitrogen fixation by the mutants was not affected by the extracellular amino acid concentration. While the radioactive
carbon flow was followed, the parent strain retained 93% of fixed14C and released only 7% into the medium. On the other hand,Anabaena ST 16 released 13% andAnabaena ST 25 released 29% into the medium. These mutants are beneficial in the production of radioactive amino acids using diazotrophic
photobiotechnology. 相似文献
57.
58.
In this study, a series of beadlike and hydrophilic supports containing reactive cyclic carbonate groups for enzyme immobilization
were prepared via reverse-phase suspension copolymerization of the aqueous solutions of vinylene carbonate (VCA), acrylamide
(AA), and N,N′-methylene bisacrylamide in paraffin oil. The supports were used as a matrix for immobilization of trypsin and showed a considerable
capacity to couple with trypsin and reasonable retention of activity for the immobilized trypsin, depending on the immobilization
conditions, such as the content of VCA structural units, reaction time, and pH of the medium. 相似文献
59.
Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-poly(methyl methacrylate) has been observed. The morphology of the diblock copolymer/Au-nanocomposite was dependent on the composition of the thiol modifier. For the thiol modifier that does not preferentially interact with one of the blocks, a perpendicular (relative to the substrate) lamellar morphology is maintained. However, for a thiol with a surfactant structure similar to one of the blocks, we observed a parallel lamellar morphology and speculate that the nanoparticles have localized at the microdomain interface. These conclusions are based on transmission electron microscopy, angle-dependent X-ray photoelectron microscopy and tensiometry. These results are consistent with theoretical predictions on the hybrid systems composed of block copolymers and nanoparticles. 相似文献
60.
血浆样品经0.01mol·L-1盐酸和无水乙醇浸取,在碱性条件下用氯仿萃取,GG-MS-选择离子测量法测定,外标法定量。在选定的色谱条件下,盐酸克仑特罗的检出限为0.05ng,线性范围为0.1-100ng,方法的平均回收率为95.6%,RSD小于6.82%(n=6)。该法毋需衍生化,基质无干扰,简便可靠,适用于生物材料中克仑特罗的快速分析。 相似文献