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排序方式: 共有206条查询结果,搜索用时 31 毫秒
71.
Giovana A. Bataglion Gustavo Henrique Martins Ferreira Souza Gabriel Heerdt Nelson H. Morgon José Diogo Lisboa Dutra Ricardo Oliveira Freire Marcos N. Eberlin Alessandra Tata 《Journal of mass spectrometry : JMS》2015,50(2):336-343
Traveling wave ion mobility mass spectrometry (TWIM‐MS) is shown to be able to separate and characterize several isomeric forms of diterpene glycosides stevioside (Stv) and rebaudioside A (RebA) that are cationized by Na+ and K+ at different sites. Determination and characterization of these coexisting isomeric species, herein termed catiomers, arising from cationization at different and highly competitive coordinating sites, is particularly challenging for glycosides. To achieve this goal, the advantage of using CO2 as a more massive and polarizable drift gas, over N2, was demonstrated. Post‐TWIM‐MS/MS experiments were used to confirm the separation. Optimization of the possible geometries and cross‐sectional calculations for mobility peak assignments were also performed. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
72.
Cortezzi SS Garcia JS Ferreira CR Braga DP Figueira RC Iaconelli A Souza GH Borges E Eberlin MN 《Analytical and bioanalytical chemistry》2011,401(4):1331-1339
A bottom-up label-free mass spectrometric proteomic strategy was used to analyse the protein profiles of the human embryonic
secretome. Culture media samples used for embryonic culture of patients undergoing intracytoplasmic sperm injection cycles
were selected as a test case for this exploratory proof-of-principle study. The media were stored after embryo transfer and
then pooled into positive (n = 8) and negative (n = 8) implantation groups. The absolute quantitative bottom-up technique employed a multidimensional protein identification
technology based on separation by nano-ultra-high pressure chromatography and identification via tandem nano-electrospray
ionization mass spectrometry with data-independent scanning in a hydrid QqTOF mass spectrometer. By applying quantitative
bottom-up proteomics, unique proteins were found exclusively in both the positive- and negative-implantation groups, which
suggest that competent embryos express and secrete unique biomarker proteins into the surrounding culture medium. The selective
monitoring of these possible secretome biomarkers could make viable procedures using single-embryo transfer. 相似文献
73.
Valérien Eberlin 《代数通讯》2013,41(1):183-191
Résumé: i1 s'agit d'étudier 1es algèbres de Lie dimensionnellement nilpotentes, en abrégé ADN, c'est à dire celles qui admettent une dérivation nilpotente de corang 1. Quand ces algèbres ne sont pas nilpotentes, Leger et Manley ont montré que ce sont des algèbres résolubles d'idéal maximal nilpotent ou sl 2. Nous montrons alors qu'il n'y a que quatre types possibles pour l'idéal maximal nilpotent et que la structure de l'idéal maximal nilpotent est presque connue. Dans le cas o[ugrave] ces ADN sont nilpotentes, nous étudions le cas o[ugrave] elles sont 2-nilpotentes. Nous décrivons les constantes de structures sur une base dite adaptée, des ADN 2-nilpotentes d'idéal dérivé de dimension 2, puis nous donnons une classification en dimension inférieure a 8 des ADN 2-nilpotentes dont l'idéal dérivé, égal au centre, est de dimension 2. Les résultats présentés sont tirés de Ia thése de l'auteur ([1]). 相似文献
74.
Campbell DI Ferreira CR Eberlin LS Cooks RG 《Analytical and bioanalytical chemistry》2012,404(2):389-398
Desorption electrospray ionization imaging allows biomarker discovery and disease diagnosis through chemical characterization of biological samples in their native environment. Optimization of experimental parameters including emitter capillary size, solvent composition, solvent flow rate, mass spectrometry scan-rate and step-size is shown here to improve the resolution available in the study of biological tissue from 180?μm to about 35?μm using an unmodified commercial mass spectrometer. Mouse brain tissue was used to optimize and measure resolution based on known morphological features and their known relationships to major phospholipid components. Features of approximately 35?μm were resolved and correlations drawn between features in grey matter (principally PS (18:0/22:6), m/z 834) and in white matter (principally ST (24:1), m/z 888). The improved spatial resolution allowed characterization of the temporal changes in lipid profiles occurring within mouse ovaries during the ovulatory cycle. An increase in the production of phosphatidylinositol (PI 38:4) m/z 885 and associated fatty acids such as arachidonic acid (FA 20:4) m/z 303 and adrenic acid (FA 22:4) m/z 331was seen with the postovulatory formation of the corpus luteum. 相似文献
75.
Cabral EC Simas RC Santos VG Queiroga CL da Cunha VS de Sá GF Daroda RJ Eberlin MN 《Journal of mass spectrometry : JMS》2012,47(1):1-6
Venturi easy ambient sonic spray ionization mass spectrometry in both its liquid (V(L) -EASI-MS) and solid sample modes (V(S) -EASI-MS) is shown to provide nearly immediate and secure typification of woods, as demonstrated for Mahogany, an endangered and most valuable type of tropical wood. This reddish wood displays unique phytochemical markers (phragmalin-type limonoids) which are rapidly detected from the wood surface by V(S) -EASI-MS or from a simple methanol extract of a tiny wood chip by V(L) -EASI-MS. Unique profiles were obtained for Mahogany (Swietenia macrophylla) whereas genuine samples of six other similar types of woods, which are commonly falsified by artificial coloring and commercialized as Mahogany, display also typical but dissimilar pythochemical profiles as compared to that of the authentic wood. Variable and atypical chemical profiles were observed for artificially colored woods. Secure chemical characterization via V(S) -EASI-MS or V(s) -EASI-MS fingerprints of Mahogany and other types of woods with similar appearance should help to control the illegal logging and trade of this and other endangered woods and their falsification, and to create certified standards. 相似文献
76.
Hlio A. Stefani Jesus M. Pena Kemilla Gueogjian Nicola Petragnani Boniek G. Vaz Marcos N. Eberlin 《Tetrahedron letters》2009,50(40):5589-5595
A variety of α,β-unsaturated aryl esters were prepared by the direct reaction of unsymmetrical aryltellurides and ethyl acrylate, catalyzed by PdCl2 via a Heck cross-coupling reaction. 相似文献
77.
Sérgio A. Saraiva Patrícia V. Abdelnur Rodrigo R. Catharino George Nunes Marcos N. Eberlin 《Rapid communications in mass spectrometry : RCM》2009,23(3):357-362
A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS). With no need for sample‐preparation or pre‐separation procedures, EASI‐MS and EASI‐MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
78.
The oxidation of geminal biaryl ethenes 3 and 1,3-enynes 5 using m-chloroperbenzoic acid in dichloromethane at room temperature presents a catalyst-free approach for the synthesis of functionalized benzophenones 4 and ynones 6, respectively. 相似文献
79.
Rodrigo O. M. A. De Souza Prof. Dr. Eduardo T. da Penha Humberto M. S. Milagre Prof. Dr. Simon J. Garden Pierre M. Esteves Marcos N. Eberlin Prof. Dr. Octavio A. C. Antunes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9799-9804
Biginelli reactions have been monitored by direct infusion electrospray ionization mass spectrometry (ESI‐MS) and key cationic intermediates involved in this three‐component reaction have been intercepted and further characterized by tandem MS experiments (ESI‐MS/MS). Density functional theory calculations were also used to investigate the feasibility of the major competing mechanisms proposed for the Biginelli reaction. The experimental and theoretical results were found to corroborate the iminium mechanism proposed by Folkers and Johnson, whereas no intermediates directly associated with either the more energy demanding Knoevenagel or enamine mechanisms could be intercepted. 相似文献
80.
Giovanni W. Amarante Mario Benassi Humberto M. S. Milagre Dr. Ataualpa A. C. Braga Dr. Feliu Maseras Dr. Marcos N. Eberlin Dr. Fernando Coelho Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(45):12460-12469
A Morita–Baylis–Hillman (MBH) reaction catalyzed by thiourea was monitored by ESI‐MS(/MS) and key intermediates were intercepted and characterized. These intermediates suggest that thiourea acts as an organocatalyst in all steps of the MBH reaction cycle, including the rate‐limiting proton‐transfer step. DFT calculations, performed for a model MBH reaction between formaldehyde and acrolein with trimethylamine as base and in the presence or the absence of thiourea, suggest that thiourea accelerates MBH reactions by decreasing the transition‐state (TS) energies through bidentate hydrogen bonding throughout the whole catalytic cycle. In the rate‐limiting proton‐transfer step, the thiourea acts not as a proton shuttle, but as a Brønsted acid stabilizing the basic oxygen center that is formed in the TS. 相似文献