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991.
Logarithmic general error distribution is an extension of lognormal distribution. In this paper, with optimal norming constants the higher-order expansion of distribution of partial maximum of logarithmic general error distribution is derived. 相似文献
992.
辅因子是蛋白质或酶结构的重要组成部分,在许多酶的功能中发挥重要乃至关键作用。在科研和教学中,现有的辅因子概念及其分类系统不够清晰准确。本文从化学本质和功能上将辅因子分为催化型、载体型和底物型3类,并以若干典型的辅因子为例讨论辅因子的特异性及再生性等问题。 相似文献
993.
Four Gadolinium Coordination Compounds Derived from Various Tetrazole‐Containing Carboxylic Acids
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Lei Shen Yu‐Ting Min Xue Bai Jing Wang Qi Wu Jie Yang Hong‐Jian Chen Fei Geng Gao‐Wen Yang Qiao‐Yun Li 《无机化学与普通化学杂志》2016,642(19):1112-1119
Reactions of four different tetrazole‐containing carboxylic acids with GdCl3 · 6H2O, produced the coordination compounds, [Gd4(pytza)5(H2O)10(μ‐O) Cl] · 4H2O · 2Cl ( 1 ) [pytza = 2‐(5‐(pyridine‐4‐yl)‐2H‐tetrazole‐2‐yl)acetato], [Gd(pztza)2(H2O)6] · pztza · 3H2O ( 2 ), [pztza = 2‐(5‐(pyrazin‐2‐yl)‐2H‐tetrazol‐2‐yl) acetato], [Gd(pmtza)2(H2O)6]Cl · 2H2O ( 3 ), [pmtza = 2‐(5‐(pyrimidyl‐2‐yl)‐2H‐tetrazol‐2‐yl) acetato], and Gd(tzpya)2(H2O)5]Cl · 4H2O ( 4 ) [tzpya = 2‐(4‐(5H‐tetrazol‐5‐yl)pyridin‐1(4H)‐yl) acetato]. The compounds were structurally characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. X‐ray diffraction analysis reveals that compound 1 displays a 2D single layered network and compounds 2 – 4 are mononuclear. Compounds 1 – 4 are self‐assembled to form 3D networks by hydrogen bonding interactions. Furthermore, the luminescent properties in the solid state at room temperature were investigated. 相似文献
994.
Xinxin Ju Tianxiang Zhao Feng Sha Bo Guo Xiaohong Xie 《Physics and Chemistry of Liquids》2016,54(3):411-421
Thermophysical property data for the binary system of 1-methoxy-2-propanol (PGME) + dimethyl sulfoxide (DMSO), a potential candidate for use as the scrubbing liquid for the absorption of SO2, are lacking in the literature. This paper presents experimental data at 0.1 MPa on the density and viscosity for this binary system measured over the whole composition range at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K. The extended combined uncertainty Uc with a 0.95 level of confidence for the pycnometer method and Ubbelohde viscometer used in this study is 0.002 g·cm?3 and 0.028 cm2·s?1, respectively. The PGME + DMSO system shows negative values of the excess molar volume at all temperatures and compositions. Based on UV-Vis and FTIR, the intermolecular interaction of PGME with DMSO was confirmed as hydrogen bonding between the hydroxyl hydrogen atom in PGME and the oxygen atom in DMSO. 相似文献
995.
Rapid screening,identification, and purification of neuraminidase inhibitors from Lithospermum erythrorhizon Sieb.et Zucc. by ultrafiltration with HPLC–ESI‐TOF‐MS combined with semipreparative HPLC
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Minmin Zhang Hengqiang Zhao Zhiguo Zhao Huijiao Yan Ruimin Lv Li Cui Jinpeng Yuan Daijie Wang Yanling Geng Daicheng Liu Xiao Wang 《Journal of separation science》2016,39(11):2097-2104
We put forward an efficient strategy based on bioassay guidance for the rapid screening, identification, and purification of the neuraminidase inhibitors from traditional Chinese medicines, and apply to the discovery of anti‐influenza components from Lithospermiun erythrorhizon Sieb.et Zucc. Ultrafiltration with high‐performance liquid chromatography and electrospray ionization time‐of‐flight mass spectrometry was employed for the rapid screening and preliminarily identification of anti‐influenza components from Zicao. Semipreparative high‐performance liquid chromatography was used for the rapid separation and purification of the target compounds. NMR spectroscopy, mass spectrometry, and UV spectroscopy were used for further structural identification, and the activity of the compounds was verified by in vitro assay. Five compounds were found to have neuraminidase inhibitory activity by this method. Subsequently, the five compounds were separated by semipreparative high‐performance liquid chromatography with the purity over 98% for all of them by high‐performance liquid chromatography test. Combined with the NMR spectroscopy, mass spectrometry, and UV spectroscopy data, they were identified as alkannin, acetylalkannin, isobutyrylalkannin, β,β‐dimethylacryloylalkannin and isovalerylalkannin. The in vitro assay showed that all five compounds had good neuraminidase inhibitory activities. These results suggested that the method is highly efficient, and it can provide platform and methodology supports for the rapid discovery of anti‐influenza active ingredients from complex Chinese herbal medicines. 相似文献
996.
Simple field‐based automated dispersive liquid–liquid microextraction of trace level phthalate esters in natural waters with gas chromatography and mass spectrometric analysis
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A small, simple, and field‐based automated dispersive liquid–liquid microextraction method followed by gas chromatography mass spectrometric analysis was developed for trace level phthalate esters analysis in natural waters. With a single syringe pump that is coupled with a multiposition valve, the whole extraction procedure including cleaning, sampling, mixing of extractant and disperser solvents, extraction, phase separation, and analytes collection was carried out in a totally automated way with a sample throughput of 21 h?1. Key factors, such as type and ratio of the extractant and disperser solvent, aspiration flow rate, extraction time, and matrix effect, were thoroughly investigated. Under the optimum conditions, linearity was found in the range from 0.03 to 60 μg/L. Limits of detection ranged from 0.0015 to 0.003 μg/L. Enrichment factors were in a range of 106–141. Reproducibility and recoveries were assessed by testing a series of three natural water samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real surface waters. The developed system is inexpensive, light (2.6 kg), simple to use, applicable in the field, with high sample throughput, and sensitive enough for trace level phthalate esters analysis in natural waters. 相似文献
997.
Qualitative screening of absorbed indoloquinazoline alkaloids and their metabolites in rat plasma after the oral administration of Wu‐Zhu‐Yu decoction by high‐resolution mass spectrometry with multiple data mining algorithms
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Huarong Xu Yajing Geng Ran Liu Ziyue Yuan Xujia Liu Qing Li Kaishun Bi 《Journal of separation science》2016,39(16):3260-3266
A rapid and sensitive liquid chromatography with high‐resolution mass spectrometry method with multiple data processing algorithms was developed and applied for the metabolite profiling of evodiamine and its analogous alkaloids in rat plasma after the administration of Wu‐Zhu‐Yu decoction. All samples were purified using hydrophilic‐lipophilic balanced solid‐phase extraction cartridges and analyzed by a Sciex TripleTOF 5600+ mass spectrometer with a 35 min liquid chromatography gradient elution. High‐resolution full‐scan mass spectrometry and information‐dependent acquisition tandem mass spectrometry data were analyzed using multiple data processing approaches. The results indicated that the detected eight prototype alkaloids could be metabolized to 58 metabolites through both phase I and phase II reactions. Oxidation was demonstrated to be the principle metabolic pathway of the parent compounds. The study contributes to the understanding of the absorption and metabolism of the alkaloids in Wu‐Zhu‐Yu decoction and provides a detailed analysis of scientific data. 相似文献
998.
Fabrication and Formation Mechanism of Ag Nanoplate‐Decorated Nanofiber Mats and Their Application in SERS
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Peng Jia Jiao Chang Jianqiang Wang Pan Zhang Bing Cao Yuting Geng Xiuxing Wang Prof. Kai Pan 《化学:亚洲杂志》2016,11(1):86-92
We report a new simple method to fabricate a highly active SERS substrate consisting of poly‐m‐phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate‐decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO3 are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface‐enhanced Raman scattering (SERS) detection of 4‐mercaptobenzoic acid (4‐MBA) with a detection limit of 10?10 m , making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals. 相似文献
999.
Min-Yan Zheng Yong-Sheng Wei Wei Geng Yuan-Zi Gu 《Molecular Crystals and Liquid Crystals》2016,630(1):19-27
A novel method of two-step esterifications was developed to synthesize compounds with asymmetric double ester groups. By using this method, six rod-like double ester compounds were prepared with p-hydroxy benzaldehyde, p-hydroxy benzoic acid bicyclohexyl carboxylic acid, cyclohexyl benzoic acid and biphenyl carboxylic acid substituted by n-propyl and n-pentyl as main reactants. The structures and properties of target compounds were confirmed by IR, MS, 1H NMR, elemental analysis, differential scanning calorimetry (DSC) and hot stage polarizing optical microscope (HS-POM). Typical yields of the target molecules were more than 70%. All the molecules have mesophases with the textures of nematic type, indicating a rod-like molecule with a longer rigid skeleton can keep its mesophases. There was no clearing point observed for any of the derivatives before they decomposed so that the temperature ranges of the mesophases could not be determined. The energy differences between frontier molecular orbitals (HOMO-LUMO) (Eg) of the compounds were calculated by cyclic voltammetry (CV). The terminal ring system has an obvious influence on the energy levels and the energy gaps (Eg). 相似文献
1000.
Geng DL Miao YH Helseth LE 《Langmuir : the ACS journal of surfaces and colloids》2007,23(16):8480-8484
We investigate the influence of salt on colloidal lithography of biomolecular patterns. Albumin labeled with fluorescein isothiocyanate (FITC) was adsorbed on polyelectrolyte-coated glass substrates covered by negatively charged colloids using fluorescence microscopy. After removing the colloids, a well-defined albumin pattern remains, and we study how the pattern changes upon adding salt to the protein solution. The proposed method is simple and cheap and can be used to create stable one- and two-dimensional biomolecular arrays. 相似文献