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101.
Solution or Gas Phase? Oxidation and Radical Formation in Electrospray Ionization Mass Spectrometry (ESI MS) 下载免费PDF全文
The relationship between one‐electron (e?) oxidation processes and the formation of radical cations of endogenous and exogenous compounds in vivo is of considerable interest. This paper reports on the experiments that allow FTICR mass spectrometric (MS) detection of ion signals that are consistent with the formation of radical cations of caffeine (CA) and theophylline (TP) during electrospray ionization (ESI) in ESI FTICR MS and in on‐line electrochemistry (EC)/ESI FTICR MS in positive mode. Significantly, the signals of the radicals of CA?+ and TP?+can be enhanced by simple modifications of the operating conditions in ESI MS, facilitating investigations of radical formation and related reactions. 相似文献
102.
Under the influence of previously published and some new theoretical results, potential‐ dependent adsorption and desorption of model electroinactive surfactants Triton X‐100 (T‐X‐100 or polyethylene glycol p‐(1,1,3,3‐tetramethylbutyl)‐phenyl ether) and sodium dodecyl sulfate (SDS) on the static mercury drop electrode (SMDE) were studied by square‐wave voltammetry (SWV). Although (according to the theory) the resulting current – potential curve should consist of two highly separated peaks, only desorption signal could be seen on each experimentally obtained voltammogram, most probably because of the limitations concerning the available potential range. Different properties of the recorded peak are in good agreement with the theory indicating that square‐wave voltammetry could be treated as a potential tool for tensammetric studies of electroinactive surface active substances. 相似文献
103.
Mass spectrometry detection of minor new meridianins from the antarctic colonial ascidians Aplidium falklandicum and Aplidium meridianum 下载免费PDF全文
Laura Núñez‐Pons Rosa María Nieto Conxita Avila Carlos Jiménez Jaime Rodríguez 《Journal of mass spectrometry : JMS》2015,50(1):103-111
Taking into account the broad biological activities found in the meridianin indole alkaloids isolated to date, we have re‐examined the organic extracts of an Antarctic collection of the tunicates Aplidium meridianum and A. falklandicum (Chordata: Ascidiacea) by HPLC in conjunction with a high‐resolution mass spectrometer (HPLC‐MS). A new set of analogs of meridianins A–G has been detected, and their structures are proposed on the basis of the molecular formulae identified by LC‐HRMS analysis using a C18 column with a gradient of water/acetonitrile and an LTQ‐FT‐MS Orbitrap detector. Remarkably, dimers derived from meridianin A and from meridianin B or E were also detected. Our findings provide further evidence of the broad variability within the meridianin‐like derivatives of this highly bioactive alkaloid family. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
104.
In this study, ent-Kaurane-3β,16β,17-triol(1) and ent-kaurane-2α,16β,17-triol(2), were isolated from the leaves of Rubus corchorifolius L. f. Their structures were elucidated based on extensive spectroscopic analysis. NMR experiments identified the two compounds and X-ray crystallographic analysis confirmed their crystal structures. The crystal of 1 belongs to monoclinic with space group P21 and a = 10.7641(3), b = 7.2789(3), c = 11.7862(4) , β = 95.275(3)°, V = 919.55(6) 3, Z = 2, C20H34O4, Mr = 322.49 g/mol, Dc = 1.230 g/m3, F(000) = 376, λ = 1.54178 , μ = 0.661 mm-1, R = 0.0319, and wR = 0.0811 for 10889 observed reflections(Ⅰ 2σ(Ⅰ)). The crystal of 2 is classified as orthorhombic with space group P212121 and a = 10.7641(3), b = 12.72224(19), c = 21.3929(3) , V = 1748.94(4) 3, Z = 4, C20H34O4, Mr = 322.47, Dc = 1.225 Mg/m3 F(000) = 712, λ = 1.54184 , μ = 0.625 mm-1, R = 0.0303 and w R = 0.0759 for 10470 observed reflections(Ⅰ 2σ(Ⅰ)). Meanwhile, the compound revealed low inhibitory activities toward Hep G2, MCF-7, and SCG-7901 cells. 相似文献
105.
分别采用共沉淀法和浸渍法、不同铁前驱物以及不同焙烧温度等研究了制备工艺对Mn-Fe/ZSM-5催化剂的结构、化学组分及NH3-SCR活性的影响。结果显示,当采用Fe(NO3)3作为Fe前驱物,并用共沉淀法制备、300°C焙烧条件下得到的MFZ-CP-N-300样品低温活性最优,在120°C时,其NO的转化率达到96.7%,120-300°C范围内NO转化率始终保持在95%以上。同时利用XRD、NH3-TPD、XPS、SEM、TEM、氮吸附等手段对催化剂结构、晶相、酸位、锰铁氧化物的化学形态及表面的形貌特征进行表征分析。结果表明锰铁氧化物分别以MnO2-Mn2O3和Fe2O3的形式高度分散于催化剂表面,特别是当Mn4+/Mn3+比例为1.254时,有较强的表面中强酸和较多的酸位数,从而增加了NH3的吸附能力,提高NO的转化率。 相似文献
106.
Direct Determination of Trace Dopamine in an Ascorbic Acid Solution at a Bare Glassy Carbon Electrode Using Differential Pulse Voltammetry 下载免费PDF全文
Lijian Sun Jing Chen Fangmin Zhao Na Liu Yingqiu Zhang Jianbo Jia Jianguo Wang 《Electroanalysis》2015,27(6):1411-1415
It is difficult to monitor dopamine (DA) accurately with a bare glassy carbon electrode because of the interference of ascorbic acid (AA). In this paper, a method for the determination of DA in an AA solution using differential pulse voltammetry was established. Because AA loses its electrochemical activity after being oxidized, hydrogen peroxide was used to oxidize AA, and the interference of AA was completely eliminated. As a result, trace DA could be directly determined in the AA solution with a bare glassy carbon electrode. When trace DA was determined in a 1.0 mmol L?1 AA solution, there was a wide linear range from 3.0×10?8 mol L?1 to 1.0×10?5 mol L?1. The application of this method was demonstrated by the selective measurement of DA in an injection without pretreatment. 相似文献
107.
Minghui Chen Zhibiao Yu Daofeng Liu Tao Peng Kun Liu Shuying Wang Yonghua Xiong Hua Wei Hengyi Xu Weihua Lai 《Analytica chimica acta》2015
Two patterns of signal amplification lateral flow immunoassay (LFIA), which used anti-mouse secondary antibody-linked gold nanoparticle (AuNP) for dual AuNP-LFIA were developed. Escherichia coli O157:H7 was selected as the model analyte. In the signal amplification direct LFIA method, anti-mouse secondary antibody-linked AuNP (anti-mouse-Ab-AuNP) was mixed with sample solution in an ELISA well, after which it was added to LFIA, which already contained anti-E. coli O157:H7 monoclonal antibody-AuNP (anti-E. coli O157:H7-mAb-AuNP) dispersed in the conjugate pad. Polyclonal antibody was the test line, and anti-mouse secondary antibody was the control line in nitrocellulose (NC) membrane. In the signal amplification indirect LFIA method, anti-mouse-Ab-AuNP was mixed with sample solution and anti-E. coli O157:H7-mAb-AuNP complex in ELISA well, creating a dual AuNP complex. This complex was added to LFIA, which had a polyclonal antibody as the test line and secondary antibody as the control line in NC membrane. The detection sensitivity of both LFIAs improved 100-fold and reached 1.14 × 103 CFU mL−1. The 28 nm and 45 nm AuNPs were demonstrated to be the optimal dual AuNP pairs. Signal amplification LFIA was perfectly applied to the detection of milk samples with E. coli O157:H7 via naked eye observation. 相似文献
108.
Cheng-Fang Wang Li Fan Mei Tian Shu-Shan Du Zhi-Wei Deng Jiang-Bin Feng 《Natural product research》2015,29(14):1380-1383
This work aimed to investigate benzophenanthridine from the roots of Zanthoxylum nitidum (Roxb.) DC. var. fastuosum How ex Huang for the first time. Thirteen benzophenanthridines were isolated, and our results of the cytotoxic activities indicated that compound 6 exhibited the best potency against A549, Hela, SMMC-7721 and EJ, with the IC50 values of 27.50, 37.50, 16.95 and 60.42 μM, respectively. Compounds 7 and 11 also showed strong cytotoxicity when tested against the four human cancer cell lines (A549, Hela, SMMC-7721 and EJ), while only compounds 12 and 13 displayed cytotoxicity in inhibiting BALL-1 proliferation among all the compounds. These results suggested that benzophenanthridines may become a valid alternative of potential basis for new anti-proliferative agents. 相似文献
109.
A novel triterpenoid 3α,16β,23,24-tetrahydroxy-28-nor-ursane-12,17,19,21-tetraen (1) was isolated from the fruits of Gardenia jasminoides var. radicans Makino. The structure of the new compounds was elucidated on the basis of spectroscopic analysis including MS and NMR data. Compound 1 was in vitro tested for cytostatic activity on human throat cancer (Hep-2) cell line by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide method and showed mild anticancer activity with the IC50 of 31.2 μM. 相似文献
110.
In this paper, for the first time, an inorganic–organic hybrid material based on ZnO nanoparticles was anchored to a composite made from polythiophene and hexagonally ordered silica (ZnO/PT/SBA-15) for use in solid-phase fibre microextraction (SPME) of medicinal plants. A homemade SPME apparatus was used for the extraction of volatile components of Ziziphora tenuior L. A simplex method was used for optimisation of five different parameters affecting the efficiency of the extraction. The main constituents extracted by ZnO/PT/SBA-15 and PDMS fibres and hydrodistillation (HD) methods, respectively, included pulegone (51.25%, 53.64% and 56.68%), limonene (6.73%, 6.58% and 8.3%), caryophyllene oxide (5.33%, 4.31% and 4.53%) and 1,8-cineole (4.21%, 3.31% and 3.18%). In comparison with the HD method, the proposed technique could equally monitor almost all the components of the sample, in an easier way, in a shorter time and requiring a much lower amount of the sample. 相似文献