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991.
Ghada H. Yassin Christian Grun Jean H. Koek Khaleel I. Assaf Nikolai Kuhnert 《Journal of mass spectrometry : JMS》2014,49(11):1086-1095
Ultra performance liquid chromatography (UPLC) when coupled to ion mobility (IMS)/orthogonal acceleration time of flight mass spectrometry is a suitable technique for analyzing complex mixtures such as the black tea thearubigins. With the aid of this advanced instrumental analysis, we were able to separate and identify different isomeric components in the complex mixture which could previously not be differentiated by a conventional high performance liquid chromatography/tandem mass spectrometry. In this study, the difference between isomeric structures theasinensins, proanthocyanidins B‐type and rutin (quercetin‐3O‐rutinoside) were studied, and these are present abundantly in many botanical sources. The differentiation between these structures was accomplished according to their acquired mobility drift times differing from the traditional investigations in mass spectrometry, where calculation of theoretical collisional cross sections allowed assignment of the individual isomeric structures. The present work demonstrates UPLC–IMS‐MS as an efficient technology for isolating and separating isobaric and isomeric structures existing in complex mixtures discriminating between them according to their characteristic fragment ions and mobility drift times. Therefore, a rational assignment of isomeric structures in many phenolic secondary metabolites based on the ion mobility data might be useful in mass spectrometry‐based structure analysis in the future. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
992.
Maria S. Tarasenko Alexandra Yu. Ledneva Nikolai G. Naumov Dmitry Y. Naumov Vladimir E. Fedorov 《Journal of Cluster Science》2005,16(3):353-365
Three novel cluster complex compounds Cs[{Me3Sn}3{Re6Se8(CN)6}] (1), [{Me3Sn(H2O)}2{Me3Sn}{Re6Se8(CN)6}] · H2O (2) and [(Me3Sn)3(OH)2][{Me3Sn}3{Re6Se8(CN)6}] (3) have been synthesized by reaction of Cs3KRe6Se8(CN)6 with SnMe3Cl in aqueous solutions at different pH values (pH ~7 for 1, pH <7 for 2 and pH >7 for 3). The crystal structures of all compounds have low dimensional features (linear chains in 1, zig-zag chains in 2; layers in 3), they are polymeric ones based on ${-}{\rm Re}_{6}{-}{\rm CN}{-}{\rm SnMe}_{3}{-}{\rm NC}{-}{\rm Re}_{6}{-}$ bonding. The connectivity of these structures is determined strongly by reaction conditions, in particular, pH of reaction solutions. 相似文献
993.
Nikolai Alov 《Analytical letters》2018,51(11):1789-1795
Novel rapid determination of copper-zinc ore elemental composition by total reflection X-ray fluorescence (TXRF) is proposed. Approaches for solid state sample analysis by TXRF are provided. The sample preparation is chosen to obtain the suspensions in ethylene glycol. The optimum suspension preparation conditions (sample mass, volume of dispersion medium) and the measurement conditions (internal standard element, spectra acquisition time) were determined. The sedimentation stability of suspensions was studied. It was found that the suspensions remain stable for approximately 2?min, which is sufficiently long for the sampling the suspension. The proposed technique allows determining the elemental composition of solid ore samples without sample digestion. The sample preparation time takes approximately 20?min. The relative standard deviation of the analytical results did not exceed 10%. 相似文献
994.
The synthesis of series of D(2h) and C(2v) symmetric oxygenated aromatic dicarboxaldehydes, using dilithiation methodology, is described along with their reactivity in the [3+3] cyclocondensation reaction with (1R,2R)-diaminocyclohexane to give oxygenated trianglimine macrocycles. Macrocycles derived from C(2v) symmetric dialdehydes give macrocycles with a stereogenic aromatic plane with complete diastereocontrol, as a mixture of rotamers. 相似文献
995.
The supramolecular self-assembly of macromonomers may serve as a first step to prepare well-defined, highly functionalized, hierarchically structured, conjugated polymers. Functional diacetylene macromonomers equipped with an oligopeptide segment designed to promote self-assembly into parallel beta-sheet type structures and a polydisperse, aliphatic coil segment to prevent global ordering give rise to supramolecular polymers with a tubular double-helical quarternary structure in organic solution. These supramolecular polymers may then be converted into the corresponding poly(diacetylene)s by UV irradiation under retention of their hierarchical structure. 相似文献
996.
Dangerfield JA Windbichler N Salmons B Günzburg WH Schröder R 《Electrophoresis》2006,27(10):1874-1877
StreptoTag is a novel affinity chromatography-based method for the isolation of high- and low-affinity RNA binding proteins. Originally it was shown possible to isolate recombinant protein from yeast or bacterial extracts using small, specific, well-characterised RNA binding targets. Here we show that using an enhanced aptamer it is not only possible to efficiently immobilise large, highly structured RNA binding targets onto the streptomycin columns but also that the StreptoTag method can be used for the isolation and purification of endogenously expressed regulatory proteins, with relatively low abundance, from eukaryotic extracts. As an example for this we uncover the identity of a karyophilic cellular protein which specifically binds to an area within the large, highly folded structure that characterises the mRNA from the unique 3' region (U3) of the mouse mammary tumour virus (MMTV) long terminal repeat (LTR). Hence, this method is now suitable for the quick and efficient isolation and identification of novel RNA binding proteins such as regulatory factors. 相似文献
997.
We show that for any δ∈[0,1) there exists a homogeneous order 2−δ analytic outside zero solution to a uniformly elliptic Hessian equation in R5. 相似文献
998.
Nikolai Chemetov Fernanda Cipriano 《Stochastic Processes and their Applications》2018,128(8):2710-2749
This article deals with a stochastic control problem for certain fluids of non-Newtonian type. More precisely, the state equation is given by the two-dimensional stochastic second grade fluids perturbed by a multiplicative white noise. The control acts through an external stochastic force and we search for a control that minimizes a cost functional. We show that the Gâteaux derivative of the control to state map is a stochastic process being the unique solution of the stochastic linearized state equation. The well-posedness of the corresponding stochastic backward adjoint equation is also established, allowing to derive the first order optimality condition. 相似文献
999.
1000.
Nikolai A. Kudryashov 《Applied mathematics and computation》2009,215(5):1990-1993
Self-similar solutions of the equations for the Burgers hierarchy are presented. 相似文献