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排序方式: 共有309条查询结果,搜索用时 31 毫秒
211.
Maiko Kusano Kei Zaitsu Hiroshi Nakayama Junichi Nakajima Kazuaki Hisatsune Takako Moriyasu Shuntaro Matsuta Munehiro Katagi Hitoshi Tsuchihashi Akira Ishii 《Journal of mass spectrometry : JMS》2015,50(3):586-591
Like many new designer drugs of abuse, synthetic cannabinoids (SC) have structural or positional isomers which may or may not all be regulated under law. Differences in acute toxicity may exist between isomers which impose further burden in the fields of forensic toxicology, medicine and legislation. Isomer differentiation therefore becomes crucial from these standpoints as new designer drugs continuously emerge with just minor positional modifications to their preexisting analogs. The aim of this study was to differentiate the positional isomers of JWH‐081. Purchased standard compounds of JWH‐081 and its positional isomers were analyzed by gas chromatography‐electron ionization‐mass spectrometry (GC‐EI‐MS) first in scan mode to investigate those isomers who could be differentiated by EI scan spectra. Isomers with identical or near‐identical EI spectra were further subjected to GC‐tandem mass spectrometry (MS/MS) analysis with appropriate precursor ions. EI scan was able to distinguish 3 of the 7 isomers: 2‐methoxy, 7‐methoxy and 8‐methoxy. The remaining isomers exhibited near‐identical spectra; hence, MS/MS was performed by selecting m/z 185 and 157 as precursor ions. 3‐Methoxy and 5‐methoxy isomers produced characteristic product ions that enabled the differentiation between them. Product ion spectrum of 6‐methoxy isomer resembled that of JWH‐081; however, the relative ion intensities were clearly different from one another. The combination of EI scan and MS/MS allowed for the regioisomeric differentiation of the targeted compounds in this study. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
212.
We study the coarse Baum–Connes conjecture for product spaces and product groups. We show that a product of CAT(0) groups, polycyclic groups and relatively hyperbolic groups which satisfy some assumptions on peripheral subgroups, satisfies the coarse Baum–Connes conjecture. For this purpose, we construct and analyze an appropriate compactification and its boundary, “corona”, of a product of proper metric spaces. 相似文献
213.
Kei-Ichi Kitahara Yuji Noguchi Satoshi Itoh Nobunao Chiba Tasuku Tohyama Kunio Nagashima Takako Hanada Isao Yoshihama Sadao Arai 《Journal of chromatography. A》2009,1216(44):7415-7421
Using an HPLC column packed with monodispersed vinylbenzeneboronic acid–divinylbenzene (V–D) copolymer resins, the elution behaviors of the mono- and disaccharides were studied under different pH mobile phases. The monodispersed V–D copolymer resins were prepared by the copolymerization of 4-vinylbenzeneboronic acid and divinylbenzene in the presence of template silica gel particles (particle size: 5 μm; pore size: 10 nm), followed by dissolution of the template silica gel using a NaOH solution. Similarly, styrene–divinylbenzene (S–D) copolymer resins as the control resins were also synthesized. The transmission electron micrographs of these polymer resins revealed a good monodispersity. The complexation behavior of the saccharides was evaluated by comparison of the peak area eluted through the V–D column for that through the S–D column. Four aldopentoses (d-ribose, d-arabinose, d-xylose, and d-lyxose) and four aldohexoses (d-glucose, d-mannose, d-galactose, and d-talose) were retained completely at pH 11.9. Especially, ribose and talose were totally retained even under acidic and neutral conditions. For the disaccharides, unlike sucrose and maltose, palatinose was completely retained in basic mobile phases. 相似文献
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216.
Masakazu Nishida Tomoko Tanaka Haruhiko Fukaya Wataru Kanematsu 《Magnetic resonance in chemistry : MRC》2014,52(4):163-171
The effects of doped low‐valence cations on the properties of the SnP2O7 proton conductor at ambient temperature are investigated from changes in solid‐state NMR spectra and nuclear magnetic relaxation times. Although the T1H values increased with decreasing acidity as a result of cation exchange, the 1H chemical shifts moved to lower field in Al‐ and In‐doped materials compared with undoped ones. Furthermore, the shifts changed to higher field in Mg‐doped materials, suggesting the existence of different protonic species in those materials. The bulk phosphate chemical shifts in the 31P dipolar‐decoupling MAS NMR spectra were very similar, regardless of the nature and amount of the doping species. On the other hand, by 1H/31P cross‐polarization MAS NMR, P2O7 signals interacting with an interstitial proton [Q1(proton)] were observed in all the undoped and doped SnP2O7, while acidic P–OH‐type phosphate signals [Q1(acid)] were additionally observed in the Mg‐doped conductor. The different affinity of the proton with the dopants and phosphates caused lower conductivity and larger activation energy in the Mg‐doped materials, compared with those in the In‐ and Al‐doped materials. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
217.
Y Ikeda M Sugiura C Fukaya K Yokoyama Y Hashimoto K Kawanishi M Moriyasu 《Chemical & pharmaceutical bulletin》1991,39(3):566-571
During the course of our screening of bioactive natural products, three new saponins named periandradulcins A (1), B (2) and C (3) were isolated as phosphodiesterase (PDE, EC 3.1.4.17) inhibitors from 80% MeOH extract of the roots of Periandra dulcis Mart. (Leguminosae) by a combination of column chromatography and reversed- and normal-phase high-performance liquid chromatography (HPLC). On the basis of 1H-, 13C- and two-dimensional nuclear magnetic resonance (NMR) spectral data and chemical evidence, their chemical structures were characterized as 3-O-beta-[alpha-L-rhamnopyranosyl(1----2)-beta-D-xylopyranosyl(1----2)-b eta-D- glucuronopyranosyl]-30-hydroxyl-25-formylolean-18-ene-22 beta-O-syringate, 3-O-beta-[alpha-L-rhamnopyranosyl(1----2)-beta-D- xylopyranosyl(1----2)-beta-D-glucuronopyranosyl]-22 beta-hydroxyl-25- formylolean-12-ene and 3-O-beta-[alpha-L-rhamnopyranosyl(1----2)-beta-D- glucopyranosyl(1----2)-beta-D-glucuronopyranosyl]-22 beta-hydroxyl-25-formylolean-18-ene, respectively. The concentrations of periandradulcins A, B and C required to give 50% inhibition (IC50 values) of PDE from bovine heart, were 0.033, 7.6 and 7.7 microM, respectively. Compound 1 was the most potent among the known PDE inhibitors; it inhibited PDE-I (IC50:0.0022 microM) twenty and forty times more effectively than PDE-II and -III, respectively. 相似文献
218.
A new type of photosensitive material using a chalcogenide-metal system can be used for recording holograms. This hologram is thin, recorded by amplitude and/or phase variations; a relief hologram is also available. It is shown that this material does not require development and fixation procedures and can be used for real-time holographic interferometry. 相似文献
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220.
We study the asymptotic distribution of the critical values of f n as n goes to infinity. Let X be a closed manifold and \({f:X \times X \to \mathbb{R}}\) be a smooth function. Define \({f_n : X^{n+1} \to \mathbb{R}}\) by \({f_n(x_1, \ldots, x_{n+1}) := \frac{1}{n}\sum f(x_i, x_{i+1})}\) . 相似文献