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排序方式: 共有434条查询结果,搜索用时 15 毫秒
121.
Wei Ren Po-Jung Jimmy Huang Prof. Dr. Meilin He Prof. Dr. Mingsheng Lyu Prof. Dr. Shujun Wang Prof. Dr. Changhai Wang Prof. Dr. Juewen Liu 《Chembiochem : a European journal of chemical biology》2020,21(9):1293-1297
In 1994, the first DNAzyme named GR5 was reported, which specifically requires Pb2+ for its RNA cleavage activity. Three years later, the 8-17 DNAzyme was isolated. The 8-17 DNAzyme and the related 17E DNAzyme are also most active with Pb2+, although other divalent metals can work as well. GR5 and 17E have the same substrate sequence, and their catalytic loops in the enzyme strands also have a few similar and conserved nucleotides. Considering these, we hypothesized that 17E might be a special form of GR5. To test this hypothesis, we performed systematic rational evolution experiments to gradually mutate GR5 toward 17E. By using the activity ratio in the presence of Pb2+ and Mg2+ for defining these two DNAzymes, the critical nucleotide was identified to be T12 in 17E for metal specificity. In addition, G9 in GR5 is a position not found in most 17E or 8-17 DNAzymes, and G9 needs to be added to rescue GR5 activity if T12 becomes a cytosine. This study highlights the links between these two classic and widely used DNAzymes, and offers new insight into the sequence–activity relationship related to metal selectivity. 相似文献
122.
反应沉淀法制备阿奇霉素药物超微粉体 总被引:4,自引:0,他引:4
利用反应沉淀法进行了阿奇霉素微粉化的实验研究,考察了NaOH溶液浓度、搅拌速度、搅拌时间和反应温度等因素对产品粒度、形貌、分散性及收率的影响. 分别采用扫描电镜(SEM)、比表面分析仪、X射线衍射仪(XRD)和红外光谱仪(FT-IR)对产品进行了分析与表征,并对微粉化产品和原料药进行了溶出性能研究. 实验结果表明,利用此方法可以制备得到平均粒径约为413 nm的无定型阿奇霉素超微粉体,与原料药相比,微粉化的阿奇霉素粉体比表面积增加了约27倍,相应地,药物的溶出性能较原料药明显改善. 相似文献
123.
Tz-Liang Kueng Cheng-Kuan Lin Tyne Liang Jimmy J.M. Tan Lih-Hsing Hsu 《Parallel Computing》2009,35(8-9):441-454
Faults in a network may take various forms such as hardware failures while a node or a link stops functioning, software errors, or even missing of transmitted packets. In this paper, we study the link-fault-tolerant capability of an n-dimensional hypercube (n-cube for short) with respect to path embedding of variable lengths in the range from the shortest to the longest. Let F be a set consisting of faulty links in a wounded n-cube Qn, in which every node is still incident to at least two fault-free links. Then we show that Qn-F has a path of any odd (resp. even) length in the range from the distance to 2n-1 (resp. 2n-2) between two arbitrary nodes even if |F|=2n-5. In order to tackle this problem, we also investigate the fault diameter of an n-cube with hybrid node and link faults. 相似文献
124.
Roberto Orrù Roberta Licheri Antonio Mario Locci Giacomo Cao Jimmy De Wilde Fabienne Lemoisson Ludo Froyen Inigo A. Beloki Alexander E. Sytschev Alexander S. Rogachev David J. Jarvis 《Microgravity science and technology》2007,19(5-6):85-89
Combustion Synthesis experiments have been performed on the ISS (International Space Station) during the Belgian taxi-flight mission ODISSEA in November 2002, in the framework of the ESA-coordinated project COSMIC (Combustion Synthesis under Microgravity Conditions). The main objective of the experiments was to investigate the general physico-chemical mechanisms of combustion synthesis processes and the formation of products microstructure. Within the combustion zone, a number of gravity-dependent phenomena occur, while other phenomena are masked by gravity. Under certain conditions, gravity-dependent secondary processes may also occur in the heat-affected zone after combustion. To study the influence of gravity, a specially dedicated reactor ensemble was designed and used in the Microgravity Science Glovebox (MSG) onboard the ISS. In this work, the experiment design is first discussed in terms of the experimental functionality and reactor ensemble integration in the MSG. To investigate microstructure formation, a sample constituted by a cylindrical portion followed by a conical one, the latter being inserted inside a massive copper block, is used. The experiment focused on the synthesis of intermetallic matrix composites (IMCs) based on the Al-Ti-B system. Depending on the composition, different intermetallic compounds (TiAl and TiAl3) can be formed as matrix phase while TiB2 represents the reinforcing particulate phase. During the ISS mission, six samples with a relatively high green density of 65%TD have successfully been processed. The influence of the composition on the combustion process will be examined. 相似文献
125.
Hauser VL Gimon DM Bonta JV Howell TA Malone RW Williams JR 《Environmental science & technology》2005,39(18):7226-7233
The technology used in landfill covers is changing, and an alternative cover called the evapotranspiration (ET) landfill cover is coming into use. Important design requirements are prescribed by Federal rules and regulations for conventional landfill covers but not for ET landfill covers. There is no accepted hydrologic model for ET landfill cover design. This paper describes ET cover requirements and design issues, and assesses the accuracy of the EPIC and HELP hydrologic models when used for hydrologic design of ET covers. We tested the models against high-quality field measurements available from lysimeters maintained by the Agricultural Research Service of the U.S. Department of Agriculture at Coshocton, Ohio, and Bushland, Texas. The HELP model produced substantial errors in estimating hydrologic variables. The EPIC model estimated ET and deep percolation with errors less than 7% and 5%, respectively, and accurately matched extreme events with an error of less than 2% of precipitation. The EPIC model is suitable for use in hydrologic design of ET landfill covers. 相似文献
126.
Kossyrev PA Yin A Cloutier SG Cardimona DA Huang D Alsing PM Xu JM 《Nano letters》2005,5(10):1978-1981
In this work we demonstrate the feasibility of electric-field tuning of the plasmonic spectrum of a novel gold nanodot array in a liquid crystal matrix. As opposed to previously reported microscopically observed near-field spectral tuning of individual gold nanoparticles, this system exhibits macroscopic far-field spectral tuning. The nanodot-liquid crystal matrix also displays strong anisotropic absorption characteristics, which can be effectively described as a collective ensemble within a composite matrix in the lateral dimension and a group of noninteracting individual particles in the normal direction. The effective medium model and the Mie theory are employed to describe the experimental results. 相似文献
127.
Blankenship JD Houseknecht JB Pal S Bush LP Grossman RB Schardl CL 《Chembiochem : a European journal of chemical biology》2005,6(6):1016-1022
Loline alkaloids are saturated pyrrolizidines with a substituted 1-amino group and an oxygen bridge between C2 and C7, and are insecticidal metabolites of plant-symbiotic fungi (endophytes). Cultures of the endophyte, Neotyphodium uncinatum, incorporated labeled L-proline and L-homoserine into the 1-aminopyrrolizidine, N-formylloline. The A-ring carbons C1-C3 and the N1 were derived from L-homoserine; the B-ring carbons C5-C8 and the ring nitrogen were derived from L-proline. Incorporation of both deuterium atoms from L-[4,4-(2H2)]homoserine and feeding tests with labeled L-methionine indicated that L-homoserine incorporation was not achieved via aspartyl semialdehyde or S-adenosylmethionine, but probably involved a highly novel N--C bond-forming gamma-substitution reaction. 相似文献
128.
Li XJ Pedrioli PG Eng J Martin D Yi EC Lee H Aebersold R 《Analytical chemistry》2004,76(13):3856-3860
We present a software tool for visualizing data obtained from analyzing complex peptide mixtures by liquid chromatography (LC) electrospray ionization (ESI) mass spectrometry (MS). The data are represented as a two-dimensional density plot. For experiments employing collision-induced dissociation (CID), links are embedded in the image to the CID spectra and the corresponding peptide sequences that are represented by the respective feature. The image provides an intuitive method to evaluate sample quality and the performance of an LC-ESI-MS system and can be used to optimize experimental conditions. Local patterns of the image can also be used to identify chemical contaminants and specific peptide features. Therefore, this software tool may have broad application in MS-based proteomics. 相似文献
129.
The uniform transparent TiO2/SiO2 photocatalytic composite thin films are prepared by sol-gel method on the soda lime glass substrates, and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), BET surface area, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the addition of SiO2 to TiO2 thin films can suppress the grain growth of TiO2 crystal, increase the hydroxyl content on the surface of TiO2 films, lower the contact angle for water on TiO2 films and enhance the hydrophilic property of TiO2 films. The super-hydrophilic TiO2/SiO2 photocatalytic composite thin films with the contact angle of 0-° are obtained by the addition of 10%-20% SiO2 in mole fraction. 相似文献
130.