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81.
Dashan Zhang Yongjun Jiang Jiaqi Li Wanjing Ding Zhe Chen Zhongjun Ma 《Tetrahedron》2018,74(42):6150-6154
Thioquinomycins A-D (1–4), four novel naphthothiophenediones were isolated from the rice-based medium of the marine-derived Streptomyces sp. SS17F. Their structures were elucidated by spectroscopic methods and HRESIMS data. The absolute configurations of all the compounds were elucidated by X-ray diffraction analysis, ECD and Mosher's method combined with 19F-NMR. Compounds 1–4 showed moderate cytotoxicity against NCI-H1975 with IC50 values from 17.5 to 50?μM. In addition, compounds 1–4 also exhibited inhibitory activities against PKCα and ROCK2 protein kinase. 相似文献
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Kai Liu Jin Sun Yongjun Wang Kun Gao Bing Wen Yuan He Zhonggui He 《Chromatographia》2008,67(9-10):833-836
A rapid and sensitive method using liquid chromatography with electrospray ionization mass spectrometric detection (LC–ESI-MS) was developed and validated for the determination of hydroxycamptothecin in rat plasma. Plasma samples were extracted with ether and separated on a C18 column interfaced with a single quadrupole mass spectrometer, with mobile phase consisting of 0.1% formic acid–methanol (45:55, v/v). Detection was carried out by positive electrospray ionization (ESI) in selected ion recording (SIR) mode at m/z 321 and 305 for hydroxycamptothecin and camptothecin (internal standard), respectively. The linearity was obtained ranged from 2.5 to 1,000 ng mL?1 and the lower limit of quantification (LLOQ) was determined to be at 2.5 ng mL?1. The intra- and inter-day precision (%RSD) was less than 5.5% and accuracy (% RE) ranged from 3.8 to 5.3%. This method was applied successfully to a preliminary pharmacokinetic study following the intravenous administration of hydroxycamptothecin to rats. 相似文献
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The aliphatic amino acids glycine, valine, leucine, and isoleucine are thermally placed into the gas phase and expanded into a vacuum system for access by time of flight mass spectroscopy and infrared (IR) spectroscopy in the energy range of 2500-4000 cm(-1) (CH, NH, OH, and stretching vibrations). The isolated neutral amino acids are ionized by a single photon of 10.5 eV energy (118 nm), which exceeds by less than 2 eV their reported ionization thresholds. As has been reported for many hydrogen bonded acid-base systems (e.g., water, ammonia, alcohol, acid clusters, and acid molecules), the amino acids undergo a structural rearrangement in the ion state (e.g., in simplest form, a proton transfer) that imparts sufficient excess vibrational energy to the ion to completely fragment it. No parent ions are observed. If the neutral ground state amino acids are exposed to IR radiation prior to ionization, an IR spectrum of the individual isomers for each amino acid can be determined by observation of the ion intensity of the different fragment mass channels. Both the IR spectrum and fragmentation patterns for individual isomers can be qualitatively identified and related to a particular isomer in each instance. Thus, each fragment ion detected presents an IR spectrum of its particular parent amino acid isomer. In some instances, the absorption of IR radiation by the neutral amino acid parent isomer increases a particular fragmentation mass channel intensity, while other fragmentation mass channel intensities decrease. This phenomenon can be rationalized by considering that with added energy in the molecule, the fragmentation channel populations can be modulated by the added vibrational energy in the rearranged ions. This observation also suggests that the IR absorption does not induce isomerization in the ground electronic state of these amino acids. These data are consistent with theoretical predictions for isolated amino acid secondary structures and can be related to previous IR spectra of amino acid conformers. 相似文献
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Back Cover: Graphene Oxide Catalyzed C−H Bond Activation: The Importance of Oxygen Functional Groups for Biaryl Construction (Angew. Chem. Int. Ed. 9/2016) 下载免费PDF全文
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为了解决系统设计中单片机串口数量较少不能同时满足多路串行通信的问题,通过对现有串口扩展技术进行对比分析,并针对水文监测系统的应用需求,提出了基于芯片XR16L784完成串口扩展的设计方案。介绍了串口扩展芯片XR16L784的硬件设计和软件编程的具体实现方法,并在水文监测系统上进行了实验验证。结果表明:串口扩展芯片XR16L784可有效实现多个串口扩充,扩充后的串口通道能够在不同波特率下稳定、可靠实现数据双向传输。串口扩展方案解决了在多路串行通信系统中系统主控单元串口数量有限的问题,在水文监测系统中体现出很好的实用价值。 相似文献
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5-甲基-7-羟基-1,3,4三氮吲哚嗪(简称稳盐TAI)作为乳剂制备过程的有机稳定剂,已得到广泛应用.一些作者发现,稳盐除了作为稳定剂之外,对部分乳剂还有增感作用.Tani[1]在硫敏化的立方体溴化银乳剂中加入稳盐,发现可使乳剂的感光度成倍增加,而稳盐对扁平颗粒和八面体颗粒的溴化银乳剂的增感效果较小. 相似文献
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维生素K3电化学反应机理的红外光谱电化学研究 总被引:2,自引:0,他引:2
用循环信安法及现场红外光谱电化学法研究了维生素K3在铂电极上,弱碱性水溶液介质中的电化学反应机理。循环伏安法实验结果显示VK3的电反应为两步电子准可逆电极过程,现场光谱电化学实验结果则从基团特征吸收频率的变化表明了VK3的电化学还原和氧化经历了从萘醌到萘酚的互变过程。据此进一步证实了VK3由萘醌到酚的电化学反应机理。 相似文献
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