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741.
Yingda Wang Shijun Qian Guangzhen Meng Shuzheng Zhang 《Applied biochemistry and biotechnology》2001,95(2):93-101
The L-asparaginase (ASN) from Escherichia coli AS1.357 was cloned as a DNA fragment generated using polymerase chain reaction technology and primers derived from conserved
regions of published ASN gene sequences. Recombinant plasmid pASN containing ASN gene and expression vector pBV220 was transformed
in different E. coli host strains. The activity and expression level of ASN in the engineering strains could reach 228 IU/mL of culture fluid
and about 50% of the total soluble cell protein respectively, more than 40-fold the enzyme activity of the wild strain. The
recombinant plasmid in E. coli AS1.357 remained stable after 72h of cultivation and 5h of heat induction without selective pressure. The ASN gene of E. coli AS1.357 was sequenced and had high homology compared to the reported data. 相似文献
742.
743.
Arrays of NiO nanoparticles have been synthesized via thermal decomposition of nickel dimethylglyoximate precursor. The structure, morphology and properties of the products were characterized by XRD, TEM, SAED and UV-vis spectrophotometry. TEM reveals that one-dimensional arrays consist of NiO nanoparticles. XRD and SAED indicate that these NiO nanoparticles crystallize with a polycrystalline structure. The optical absorption band gap of NiO nanoparticles is 3.51 eV. 相似文献
744.
In this paper, a false color image fusion method for merging visible and infrared images is proposed. Firstly, the source images and reference image are decomposed respectively by Laplacian pyramid transform. Then the grayscale fused image and the difference images between the normalized source images are assigned to construct YCBCR components. In the color transfer step, all the three channels of the color space in each decomposition level are processed with the statistic color mapping according to the color characteristics of the corresponding sub-images of the reference image. Color transfer is designed based on the multi-resolution scheme in order to significantly improve the detailed information of the final image, and to reduce excessive saturation phenomenon to have a comparatively natural color appearance compared with the classical global-coloring algorithm. Moreover, the differencing operation between the normalized source images not only provides inter-sensor contrast to make popping the potential targets but also weakens the influence of the ambient illumination variety to a certain degree. Finally, the fused results and several metrics for evaluation of fused images subjectively and objectively illustrate that the proposed color image fusion algorithm can yield a more complete mental representation of the perceived scene, resulting in better situational awareness. 相似文献
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746.
747.
748.
The influences of pH and NaCl concentration of dipping solutions and the pH and NaCl concentration of disintegration solutions on the disintegration behaviors of poly(4-vinylpyridiniomethanecarboxylate) (PVPMC)/poly(sodium 4-styrenesulfonate) (PSS) (PVPMC/PSS) multilayer films were investigated by ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), quartz crystal microbalance (QCM) and atomic force microscopy (AFM). It was found that the disintegration rates and degrees of PVPMC/PSS multilayer films in neutral water could be well controlled by changing pH of dipping solutions and immersion time during the disintegration process. Furthermore, PVPMC/PSS multilayer films could be disintegrated completely and rapidly in pH 8 alkali solution or physiological condition (i.e., 0.15 M NaCl solution). The controllable disintegration of PVPMC/PSS multilayer films was then utilized to fabricate PEC/PSS free-standing multilayer films, in which PEC was a positively charged polyelectrolyte complex made from excessive poly(diallyldimethylammonium) (PDDA) and PSS. The experimental results indicated that the disintegration rates of PVPMC/PSS sacrificial sublayer strongly affected the integrity of the resultant PEC/PSS free-standing multilayer films. Only free-floating PEC/PSS was released from neutral water by disintegrating PVPMC/PSS multilayer sublayers. However, large size flat and tube-like PEC/PSS free-standing multilayer films with good mechanical properties were obtained facilely from pH 8 alkali solution and 0.15 M NaCl solution, respectively. The preparation of such free-standing films at physiological condition may be useful in the biological or medical application. 相似文献
749.
Hua Li Siwang Wang Qian Yang Yanhua Xie Wei Cao Bangle Zhang Jianbo Wang Jiepin Wang Meng Wang 《Chromatographia》2011,73(5-6):495-500
Paeonol, an important constituent of the traditional Chinese medicine Cortex Moutan, has a variety of bioactivity. A simple and sensitive HPLC?CUV method has been developed for analysis of paeonol in different rat tissue (heart, liver, spleen, lung, kidney, and brain). Bio-samples were prepared by simple protein precipitation, and separation of paeonol was achieved on a C18 column with methanol?C2% glacial acetic acid solution 70:30 (v/v) as mobile phase at a flow rate of 1.0 mL min?1. UV detection was at 274 nm and the column temperature was 30 °C. Linearity was good between 0.025 and 5.0 ??g mL?1 (r 2 ?? 0.9990) for tissue samples. Inter-day and intra-day accuracy (as relative error, RE) and precision (as relative standard deviation, RSD) were <5.94 and 6.05%, respectively. The limit of detection was 0.025 ??g mL?1 and extraction recovery for all samples was ??85.86%. The method was successfully applied to a tissue-distribution study after oral administration of 40 mg kg?1 paeonol to healthy Sprague?CDawley rats. The study showed that paeonol was quickly distributed and eliminated after oral administration; liver and kidney were the major distribution tissues of paeonol in rats, and paeonol quickly passed through the blood?Cbrain barrier. It was also found there was no long-term accumulation of paeonol in rat tissues. 相似文献
750.
Dr. Xin Fang Ying Tong Di Yu Zhang Dr. Zhi Ping Xu Prof. Yang Lu Qian Qian Chen Prof. Qi Tai Zheng Prof. Dr. Xiao Jiang Hao 《Angewandte Chemie (International ed. in English)》2015,54(19):5592-5595
Perforalactone A ( 1 ), a new 20S quassinoid with a unique cagelike 2,4‐dioxaadamantane ring system and a migrated side chain, was isolated from the plant Harrisonia perforata together with two biosynthetically related new quassinoids. The structures of these natural products were elucidated by NMR spectroscopy, X‐ray diffraction analysis, computational modeling, and the CD excitation chirality method. The compounds exhibited notable biological properties, including insecticidal activity against Aphis medicaginis Koch and antagonist activity at the nicotinic acetylcholine receptor of Drosophila melanogaster. The structural features of these compounds may be related to their promising biological characteristics. Their biosynthesis and an alternative origin of quassinoid‐type natural products are also discussed. 相似文献