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排序方式: 共有873条查询结果,搜索用时 250 毫秒
71.
Chemical investigations of the Australian marine sponge Ecionemia geodides resulted in the isolation of two new pyridoacridine alkaloids, ecionines A (1) and B (2), along with the previously isolated marine natural products, biemnadin (3) and meridine (4). Compounds 1 and 2 both contain an imine moiety, which is rare for the pyridoacridine structure class. The chemical structures of 1 and 2 were determined by extensive 1D and 2D NMR and MS data analyses. All compounds were tested against a panel of human bladder cancer cell lines, the increasingly metastatic TSU-Pr1 series (TSU-Pr1, TSU-Pr1-B1 and TSU-Pr1-B2) and the superficial bladder cancer cell line 5637. Ecionine A (1) displayed cytotoxicity against all cell lines, with IC50 values ranging from 3 to 7 μM. This is the first report of chemistry from the sponge genus Ecionemia. 相似文献
72.
Eduardo Laborda Emma I. Rogers Francisco Martínez‐Ortiz Ángela Molina Richard G. Compton 《Electroanalysis》2010,22(23):2784-2793
The application of additive differential pulse voltammetry to the study of the kinetics of a charge transfer process is studied. A simple analytical solution is presented, valid for spherical electrodes of any size and for electrode processes of any reversibility. From this solution, valuable diagnostic criteria for the elucidation of the electrochemical reversibility are established based on the variation of the ADPV signal with the duration of the potential pulses, the electrode radius and the pulse height. Working curves for the determination of the kinetic parameters are also given. The value of the ADPV technique is experimentally demonstrated by studying the kinetics of the reduction of 3‐nitrophenolate? and europium3+ at mercury hemispherical microelectrodes. 相似文献
73.
Emma E. McCabe 《Journal of solid state chemistry》2010,183(3):624-143
The new phases Ba2LaMNb4O15: M=Mn, Fe were prepared by solid state reaction at 1100 °C. They have the tetragonal tungsten bronze structure, space group P4/mbm, at room temperature. The two octahedral sites show partial order of M and Nb with preferential occupancy of the smaller B(1) sites by M. Both phases have high permittivities 90±15 over the range 10-320 K. Ba2LaFeNb4O15 is highly insulating with bulk conductivity ?10−8 ohm−1 cm−1 at 25 °C and tan δ?0.001 over the range 100-320 K and at 105 Hz. Solid solutions between these new phases and the compositionally and structurally related relaxor ferroelectric Ba2LaTi2Nb3O15 show gradual loss of ferroelectric behaviour attributed to replacement of polarisable Ti4+ by a mixture of (Mn, Fe)3+ and Nb5+. 相似文献
74.
Yunsen Li Emma Arigi Heather Eichert Steven B. Levery 《Journal of mass spectrometry : JMS》2010,45(5):504-519
A method for generation of novel fluorocarbon derivatives of glycosphingolipids (GSLs) with high affinity for fluorocarbon phases has been developed, and their potential applications to mass spectrometry (MS)‐based methodologies for glycosphingolipidomics have been investigated. Sphingolipid ceramide N‐deacylase (SCDase) is used to remove the fatty acid from the ceramide moiety, after which a fluorocarbon‐rich substituent (F‐Tag) is incorporated at the free amine of the sphingoid. In initial trials, a neutral GSL, globotriaosylceramide (Gb3Cer), three purified bovine brain gangliosides, and four fungal glycosylinositol phosphorylceramides (GIPCs) were de‐N‐acylated, derivatized by prototype F‐Tags, and recovered by solid phase extraction on fluorocarbon‐derivatized silica (F‐SPE). The efficacy of SCDase treatment of GIPCs was here demonstrated for the first time. Compatibility with subsequent per‐N,O‐methylation was established for the F‐tagged Gb3 Cer and purified gangliosides, and extensive mass spectra (MS1 and MS2) consistent with all of the expected products were acquired. The potential use of F‐tagged derivatives for a comprehensive MS based profiling application was then demonstrated on a crude ganglioside mixture extracted from bovine brain. Finally, a simple trial in microarray format demonstrated fixation of F‐tagged GM1 ganglioside to a fluorous glass surface, with the glycan intact and available for interaction with a fluorescent derivative of cholera toxin B chain. The methods described thus provide a new avenue for rapid GSL recovery or cleanup, potentially compatible with a variety of platforms for mass spectrometric profiling and structure analysis, as well as parallel analysis of functional interactions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
75.
Wallace EV Stoddart D Heron AJ Mikhailova E Maglia G Donohoe TJ Bayley H 《Chemical communications (Cambridge, England)》2010,46(43):8195-8197
Two DNA bases, 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (hmC), marks of epigenetic modification, are recognized in immobilized DNA strands and distinguished from G, A, T and C by nanopore current recording. Therefore, if further aspects of nanopore sequencing can be addressed, the approach will provide a means to locate epigenetic modifications in unamplified genomic DNA. 相似文献
76.
This paper reports the results of a large scale, detailed acoustic survey of 42 open plan classrooms of varying design in the UK each of which contained between 2 and 14 teaching areas or classbases. The objective survey procedure, which was designed specifically for use in open plan classrooms, is described. The acoustic measurements relating to speech intelligibility within a classbase, including ambient noise level, intrusive noise level, speech to noise ratio, speech transmission index, and reverberation time, are presented. The effects on speech intelligibility of critical physical design variables, such as the number of classbases within an open plan unit and the selection of acoustic finishes for control of reverberation, are examined. This analysis enables limitations of open plan classrooms to be discussed and acoustic design guidelines to be developed to ensure good listening conditions. The types of teaching activity to provide adequate acoustic conditions, plus the speech intelligibility requirements of younger children, are also discussed. 相似文献
77.
We show that all superconformal harmonic immersions from genus one surfaces into de Sitter spaces $S^{2n}_{1}$ with globally defined harmonic sequence are of finite-type and hence result merely from solving a pair of ordinary differential equations. As an application, we prove that all Willmore tori in $S^{3}$ without umbilic points can be constructed in this simple way. 相似文献
78.
A question of flow around an obstacle leads to an optimal control problem. If an optimum path exists, then it is calculable from the Pontryagin principle. The optimum is verified to be reached, using a discretization of the problem. 相似文献
79.
Luke J. Batchelor Emma Fitzgerald Dr. Joanna Wolowska Dr. Joseph J. W. McDouall Prof. Eric J. L. McInnes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(36):11082-11088
The synthesis, structural and magnetic characterisation of [VIII3O(tmme)2(diimine)2Cl] [diimine=2,2′‐bipyridine ( 1 ) or 1,10‐phenanthroline ( 2 )] and (HNEt3)2[VIII4O(tmme)4] ( 3 ) is reported, in which H3tmme is tris(mercaptomethyl)ethane, MeC(CH2SH)3, the thiol analogue of the famous tripodal alcohol ligands typified by H3thme [tris(hydroxymethyl)ethane, MeC(CH2OH)3]. Complexes 1 and 3 have “T‐shaped” and square topologies, respectively, and the latter is centred on a rare example of a square‐planar oxide. The tri‐thiolate ligands bind the periphery of the clusters and provide such strong antiferromagnetic exchange pathways that in both cases only a single total spin state is occupied up to room temperature, in the absence of metal–metal bonding. Magnetic data, electronic structure calculations and electrochemical data are reported. 相似文献
80.