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21.
Albert Koulman Gary Woffendin Vinod K. Narayana Helen Welchman Catharina Crone Dietrich A. Volmer 《Rapid communications in mass spectrometry : RCM》2009,23(10):1411-1418
Most analytical methods in metabolomics are based on one of two strategies. The first strategy is aimed at specifically analysing a limited number of known metabolites or compound classes. Alternatively, an unbiased approach can be used for profiling as many features as possible in a given metabolome without prior knowledge of the identity of these features. Using high‐resolution mass spectrometry with instruments capable of measuring m/z ratios with sufficiently low mass measurement uncertainties and simultaneous high scan speeds, it is possible to combine these two strategies, allowing unbiased profiling of biological samples and targeted analysis of specific compounds at the same time without compromises. Such high mass accuracy and mass resolving power reduces the number of candidate metabolites occupying the same retention time and m/z ratio space to a minimum. In this study, we demonstrate how targeted analysis of phospholipids as well as unbiased profiling is achievable using a benchtop orbitrap instrument after high‐speed reversed‐phase chromatography. The ability to apply both strategies in one experiment is an important step forward in comprehensive analysis of the metabolome. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
22.
Xinlai Cheng Hamed Alborzinia Karl-Heinz Merz Herbert Steinbeisser Ralf Mrowka Catharina Scholl Igor Kitanovic Gerhard Eisenbrand Stefan Wölfl 《Chemistry & biology》2012,19(11):1423-1436
Highlights? Inhibition of TGFβ/BMP signaling by degradation of nonactivated R-Smads ? Total R-Smad pools are regulated through the ubiquitin-proteasome pathway ? Ubiquitin proteases USP9x and USP34 interact directly with R-Smads ? Indirubin derivative E738 controls BMP/TGFβ signaling though R-Smad depletion 相似文献
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Kava (Piper methysticum) dietary products have been sold worldwide for treatment of nervous anxiety, tension, and restlessness. Recent reports showed potential association of kava usage and liver injuries. This study was conducted to develop simple and reliable methodologies for the extraction and determination of 6 major kavalactones: (+)-methysticin, (+)-dihydromethysticin, (+)-kavain, (+)-dihydrokavain, yangonin, and desmethoxyyangonin. Ultrasonic extraction techniques and isocratic reversed-phase liquid chromatography (LC) were optimized for different types of samples, including capsules containing kava root extract or root powder, raw root material, tea bags, and snack bar. A suitable internal standard, 5,7-dihydroxyflavone, was used for LC calibration. Kavalactones were completely separated in 30 min using a Luna C18-2 column at 60 degrees C with an isocratic mobile phase consisting of 2-propanol-acetonitrile-water-acetic acid (16 + 16 + 68 + 0.1, v/v/v/v). Within-laboratory, intraday, and interday method variation (% relative standard deviation) for most samples extracted by methanol or methanol-water mixture were <5%. Lower levels of kavalactone contents and higher variations were observed for tea bags from water extraction or infusion as compared to methanol extraction. Labeling information of tea bags based on methanol extraction could be misleading to consumers. Analytical recoveries of snack bar fortified at 10 and 20 microg/g were >84% with RSD values <8%. Methods developed in this study offer a simple and reproducible means for analysis of kavalactones in various matrixes of dietary products. 相似文献
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Catharina C. Quitmann Victor Bezugly Frank R. Wagner Klaus Müller‐Buschbaum 《无机化学与普通化学杂志》2006,632(7):1173-1186
Solvent free high‐temperature oxidations of rare earth metals with the heterocycle pyrazole as well as in low to non‐coordinating solvents were investigated to isolate intermediate stages between monomeric and polymeric pyrazolates of the lanthanides. Reaction conditions were tuned according to simultaneous DTA/TG and temperature dependent X‐ray powder diffraction experiments on known monomeric and polymeric pyrazolates, that gave rise to the idea that further structure intermediates could be isolated. Reactions in 1,2,3,4‐tetrahydroquinoline gave the dimeric complex [Gd2(Pz)6(PzH)4](PzH)(Tech) ( 1 ) as well as the triangular complex [Nd3(Pz)9(PzH)2](PzH)(Tech)2 ( 2 ). The solvent free melt synthesis resulted in a new polymeric form of ( 3 ) (pyrazole, PzH = C3H3NNH; pyrazolate anion, Pz? = C3H3NN?; 1,2,3,4‐tetrahydroquinoline, Tech = C9H13N). All three compounds contain coordinating pyrazolate amide groups and pyrazole molecules the latter decreasing in numbers upon condensation of the building units. According to simultaneous DTA/TG/MS investigations the condensation process can be identified with the release of pyrazole molecules. 1 consists of dimeric molecules containing trivalent gadolinium with a C.N. of eight. The two gadolinium atoms show different coordination polyhedra. Only σ coordination and bridging is found for 1 . 2 consists of trimeric molecules containing trivalent neodymium. The neodymium atoms also exhibit different coordination polyhedra with C.N.s of eight and nine. Both π and σ coordination is found for 2 , the π coordinating pyrazolate ligands acting as lids of the triangular units. Topological analysis of the electron localization function (ELF) for 2 calculated at the scalar‐relativistic DFT level reveals only weakly covalent π donor η5‐Pz–Nd interactions compared to the stronger covalent σ donor Pz–Nd interactions. The topological analysis of both, the ELF and the electron density reveals no significant differences of the respective charges of the Nd atoms. 3 exhibits a one‐dimensional chain structure with EuII and a C.N of ten. It can thus be addressed the β form of the referring formula with a new arrangement of the coordinating ligands. Like the α form 3 shows σ and π coordination of pyrazole and pyrazolate ligands. Simultaneous DTA/TG analysis reveals that the low‐temperature α form shows a phase transition into the β form between 110 °C and 130 °C. The three compounds were investigated by low‐temperature single crystal X‐ray analysis, Mid IR and Far IR spectroscopy. 相似文献
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o-Iodoxybenzoic acid (IBX) was found to mediate the conversion of alpha-alkynyl alcohols into Z-enediones under notably mild conditions via a novel rearrangement mechanism (33-65% yield, 13 examples). 相似文献
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This is the second of a series of four papers studying various generalisations of Khovanov's diagram algebra. In this paper
we develop the general theory of Khovanov's diagrammatically defined “projective functors” in our setting. As an application,
we give a direct proof of the fact that the quasi-hereditary covers of generalised Khovanov algebras are Koszul. 相似文献
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The compounds [Ln(NC12H8)2], Ln = Eu and Yb, were obtained in solvent free reactions of the rare earth elements europium and ytterbium with the amine carbazole. Single crystals of both compounds were grown from the melt syntheses, no recrystallization from solvents was necessary. The new compounds are the first examples of homoleptic carbazolates of the rare earth elements furthermore exhibiting divalent lanthanides. In absence of any solvent, carbazole as the sole coordination partner shows η6‐π‐coordination in addition to the μ1‐ and μ2‐coordination of the nitrogen atoms. This results in a one‐dimensional chain structure of dimers with a formal C.N. of 6 for the rare earth elements and thus being low for divalent lanthanides. The products were investigated by X‐ray single crystal and powder diffraction, Mid IR, Far IR and Raman spectroscopy, and with DTA/TG regarding their thermal behaviour. Both compounds [Ln(NC12H8)2], Ln = Eu (1) and Yb (2) , crystallize isotypic in the triclinic space group P1. 相似文献