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921.
922.
Hao Bin Wu Prof. Xiong Wen Lou Prof. Huey Hoon Hng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):2094-2099
Layered protonated titanates (LPTs), a class of interesting inorganic layered materials, have been widely studied because of their many unique properties and their use as precursors to many important TiO2‐based functional materials. In this work, we have developed a facile solvothermal method to synthesize hierarchical spheres (HSs) assembled from ultrathin LPT nanosheets. These LPT hierarchical spheres possess a porous structure with a large specific surface area and high stability. Importantly, the size and morphology of the LPT hierarchical spheres are easily tunable by varying the synthesis conditions. These LPT HSs can be easily converted to anatase TiO2 HSs without significant structural alteration. Depending on the calcination atmosphere of air or N2, pure anatase TiO2 HSs or carbon‐supported TiO2 HSs, respectively, can be obtained. Remarkably, both types of TiO2 HSs manifest excellent cyclability and rate capability when evaluated as anode materials for high‐power lithium‐ion batteries. 相似文献
923.
An optimal control problem governed by semilinear elliptic partial differential equation is considered. The equation is in divergence form with the leading term containing controls. A relaxed problem is constructed by homogenization. By studying the G-closure problem, a local representation of admissible set of relaxed control is given. Finally, the maximum principle of relaxed problem is established via homogenization spike variation. 相似文献
924.
Flavonoids belong to a class of plant secondary metabolites that have a polyphenol structure. Flavonoids show extensive biological activity, such as antioxidative, anti-inflammatory, anti-mutagenic, anti-cancer, and antibacterial properties, so they are widely used in the food, pharmaceutical, and nutraceutical industries. However, traditional sources of flavonoids are no longer sufficient to meet current demands. In recent years, with the clarification of the biosynthetic pathway of flavonoids and the development of synthetic biology, it has become possible to use synthetic metabolic engineering methods with microorganisms as hosts to produce flavonoids. This article mainly reviews the biosynthetic pathways of flavonoids and the development of microbial expression systems for the production of flavonoids in order to provide a useful reference for further research on synthetic metabolic engineering of flavonoids. Meanwhile, the application of co-culture systems in the biosynthesis of flavonoids is emphasized in this review. 相似文献
925.
Yi Xiao Dr. Kory J. I. Plakos Xinhui Lou Dr. Ryan J. White Dr. Jiangrong Qian Dr. Kevin W. Plaxco Prof. H. Tom Soh Prof. 《Angewandte Chemie (International ed. in English)》2009,48(24):4354-4358
Singled out for its singularity : In a single‐step, single‐component, fluorescence‐based method for the detection of single‐nucleotide polymorphisms at room temperature, the sensor is comprised of a single, self‐complementary DNA strand that forms a triple‐stem structure. The large conformational change that occurs upon binding to perfectly matched (PM) targets results in a significant increase in fluorescence (see picture; F=fluorophore, Q=quencher).
926.
To obtain extracellular and high-level expression of the Dictyoglomus thermophilum Rt46B.1 xylanase B gene, this gene was integrated into the α-amylase gene site of a host strain of Bacillus subtilis WB800. The extreme thermophile xylanase gene was successfully integrated and expressed in the host, measured at 24 ± 0.4 XUs/mL
in the Luria broth medium supernatant. The recombinant enzyme was purified by ammonium sulfate precipitation, anion exchange
chromatography, and gel filtration. The molecular mass and pI value of xylanase were estimated to be 24 kDa and 4.3, respectively. The optimal pH level and temperature of the purified
enzyme were 6.5 and 85 °C, respectively. Xylanase showed reasonable activity at temperatures up to 95 °C and remained stable
at 4 °C for 1 week. The purified enzyme retained most of its activity in 1 mM ethylenediaminetetraacetic acid or dithiothreitol
and 0.1% Tween-20 or Triton X-100. However, strong inhibition was observed in the presence of 5 mM Mn2+, 0.5% sodium dodecyl sulfate, Tween-20, or Triton X-100; a strong stimulating effect was also observed in the presence of
Fe2+. The K
m and V
max values of the recombinant xylanase for birchwood xylan were calculated to be 2.417 ± 0.36 mg/mL and 325 ± 41 μmol/min mg,
respectively. Xylanase was found to be useful in the prebleaching process of paper pulps. 相似文献
927.
Zaixiang Lou Hongxin WangSong Zhu Ming ZhangYang Gao Chaoyang MaZhouping Wang 《Journal of chromatography. A》2010,1217(16):2441-2446
The simultaneous ultrasonic and microwave assisted extraction (UMAE) technique was first employed to obtain phenolics. The effects of UMAE variables including extraction time, microwave power, and solvent to solid radio on the yield of phenolics were investigated. The optimized conditions were as follows: solvent to solid ratio was 20:1 (ml/g), extraction time was 30 s, microwave power was 500 W and two times of extraction. Moreover, the phenolic yield of UMAE was higher than that by maceration, indicating a significant reduction of extraction time and an improvement of efficiency. The phenomenon is related to the strong disruption of leaf tissue structure by microwave induced expansion and ultrasonic shaking, which had been observed with the scanning electron microscopy. The phenolic compositions of the extract was then identified by ultra performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS), 10 compounds had been characterized, providing a more complete identification of phenolic compounds in burdock leaves than previously reported. The occurrence of benzoic acid and p-coumaric acid is reported for the first time. This study suggests that UMAE is a good alternative for the extraction of phenolics, with a great potential for industrial application. Also, UMAE provides a new sample preparation technique for characterization of the phenolic compounds from plants. 相似文献
928.
Peng Wang Baibiao Huang Prof. Dr. Zaizhu Lou Xiaoyang Zhang Xiaoyan Qin Ying Dai Prof. Dr. Zhaoke Zheng Xiaoning Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):538-544
By means of a simple ion‐exchange process (using different precursors) and a light‐induced chemical reduction reaction, highly efficient Ag@AgCl plasmonic photocatalysts with various self‐assembled structures—including microrods, irregular balls, and hollow spheres—have been fabricated. All the obtained Ag@AgCl catalysts were characterized by means of X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and UV‐visible diffuse reflectance spectroscopy. The effect of the different morphologies on the properties of the photocatalysts was studied. The average content of elemental Ag in Ag@AgCl was found to be about 3.2 mol %. All the catalysts show strong absorption in the visible‐light region. The obtained Ag@AgCl samples exhibit enhanced photocatalytic activity for the degradation of organic contaminants under visible‐light irradiation. The stability of the plasmonic photocatalysts was also investigated in detail. 相似文献
929.
Five molecularly imprinted polymers (MIPs) were synthesized for a large molecule, avermectin, using different preparation techniques, monomers, and polymerization solvents. Selectivities (α) of each were compared using HPLC and different mobile phases containing various levels of acetic acid. Selectivity (α) for avermectin was greatest (α estimated ≥18) when the polymer was prepared non-covalently (utilizing only non-covalent interactions between avermectin and monomer) in chloroform using methacrylic acid (MAA) monomer and evaluated in chloroform. When evaluated in acetonitrile, an MIP prepared in acetonitrile provided better selectivity (α=8.4) than the polymer prepared in chloroform. Optimizing mobile phase conditions by adding acetic acid was much more important when MIPs were evaluated in chloroform than in acetonitrile. MIPs prepared with MAA provided better selectivity than a polymer prepared with acrylamide monomer. Covalent preparation of two MIPs utilizing a covalent bond between avermectin and monomer before polymerization did not improve selectivity but did improve peak shape in chromatograms. Specificity was demonstrated by comparing the selectivity of avermectin with eprinomectin (α=3.0), a compound with a very similar structure. Results indicate that an MIP can be prepared for the large avermectin molecule, and has the potential to simplify sample preparation and to reduce the time needed for analysis. 相似文献
930.
Qian Y Shi J Chen Y Lou L Cui X Cao R Li P Tang J 《Molecules (Basel, Switzerland)》2010,15(11):8518-8533
The transformation of phosphorus (P) is a major factor of lake eutrophication, and phosphate releasing bacteria play an important role in the release process. Experiments were conducted to investigate P content and characterize phosphate solubilizing bacterial composition at the molecular level in a shallow eutrophic lake and a wetland. Results showed that P concentrations were relatively high and derived from agricultural runoff and domestic or industrial pollution. Enumeration and molecular identification of these strains indicated that these bacterial groups were abundant in the ecosystem and various kinds of bacteria participated in the phosphorus release process. Twelve phosphate solubilizing bacteria, including eight organic P-solubilizing bacteria (OPBs) and four inorganic P-solubilizing bacteria (IPBs), which belonged to three different families, were isolated and identified. Cupriavidus basilensis was found for the first time to have the ability to mineralize organic P (OP). Laboratory tests on P release ability revealed that IPBs were more effective at releasing P than OPBs. The most efficient IPB strain could accumulate over 170 mg·L-1 orthophosphate, while the equivalent OPB strain only liberated less than 4 mg·L-1 orthophosphate in liquid culture. The results obtained from this investigation should help clarify the roles of microorganisms in aquatic systems and the mechanisms of eutrophication. 相似文献