排序方式: 共有51条查询结果,搜索用时 15 毫秒
21.
Julien Marcoux Eric Thierry Corinne Vivès Luca Signor Franck Fieschi Eric Forest 《Journal of the American Society for Mass Spectrometry》2010,21(1):76-79
Structural studies of proteins by hydrogen/deuterium exchange coupled to mass spectrometry (DXMS) require the use of proteases
working at acidic pH and low temperatures. The spatial resolution of this technique can be improved by combining several acidic
proteases, each generating a set of different peptides. Three commercial aspartic proteases are used, namely, pepsin, and
proteases XIII and XVIII. However, given their low purity, high enzyme/protein ratios have to be used with proteases XIII
and XVIII. In the present work, we investigate the activity of two alternative acidic proteases from Plasmodium falciparum under different pH and temperature conditions. Peptide mapping of four different proteins after digestion with pepsin, plasmepsin
2 (PSM2), and plasmepsin 4 (PSM4) were compared. PSM4 is inactive at pH 2.2 and 0°C, making it unusable for DXMS studies.
However, PSM2 showed low but reproducible activity under DXMS conditions. It displayed no substrate specificity and, like
pepsin, no strict sequence specificity. Altogether, these results show that PSM2 but not PSM4 is a potential new tool for
DXMS studies. 相似文献
22.
23.
24.
Ouellet SG Roy A Molinaro C Angelaud R Marcoux JF O'Shea PD Davies IW 《The Journal of organic chemistry》2011,76(5):1436-1439
In this report, we disclose our findings regarding the remarkable effect of a low-level impurity found in the solvent used for a ruthenium-catalyzed direct arylation reaction. This discovery allowed for the development of a robust and high-yield arylation protocol that was demonstrated on a multikilogram scale using carboxylate as the cocatalyst. Finally, a practical, scalable, and chromatography-free synthesis of the biaryl core of Anacetrapib is described. 相似文献
25.
26.
27.
[reaction: see text] The stereoselective displacement of a variety of chiral benzylic alcohols with triethylmethanetricarboxylate (TEMT) under Mitsunobu conditions (DEAD, PMe(3)) has been demonstrated to proceed in good yield (70-94%) and with a high degree of inversion. Subsequent saponification and decarboxylation of the products thus obtained provide chiral 3-aryl-3-substituted propanoic acids without racemization. 相似文献
28.
Davies IW Marcoux JF Taylor JD Dormer PG Deeth RJ Marcotte FA Hughes DL Reider PJ 《Organic letters》2002,4(3):439-441
Addition of methyl acetoacetate to 2-nitrovinamidinium hexafluorophosphate salts leads to the formation of anilines or phenols in good to excellent yields depending on the alkylamine substituents. Small substituents, e.g., pyrrolidine, lead to the formation of anilines while large substituents, e.g., N,N-diisopropyl, exclusively give phenols. Labeling studies implicate a [1,5]-H shift proceeding with excellent isotopic fidelity. 相似文献
29.
Davies IW Marcoux JF Kuethe JT Lankshear MD Taylor JD Tsou N Dormer PG Hughes DL Houk KN Guner V 《The Journal of organic chemistry》2004,69(4):1298-1308
Tri- and tetrasubstituted anilines are formed in good to excellent yields by the addition of ketones to vinamidinium salts (up to 98%). The reaction proceeds via the formation of dienone intermediates, which react to form an enamine with the liberated amine. In the case of a nitro, or dimethylaminomethylene substituent, the enamines undergo a facile electrocyclic ring closure to form a cyclohexadiene, which goes on to form anilines with a high degree of selectivity (up to 50:1) with a minor competing pathway proceeding via the enol providing phenols. Competition experiments using isotopic substitution reveal that the rate determining step en route to dienone is enol/enolate addition to the vinamidinium salt, which is characterized by an inverse secondary isotope effect (k(H/D) 0.7-0.9). Computational studies have been used to provide a framework for understanding the reaction pathway. The original proposal for a [1,5]-H shift was ruled out on the basis of the calculations, which did not locate a thermally accessible transition state. The minimum energy conformation of the enamine is such that a facile electrocyclic ring closure is ensured, which is corroborated by the experimental studies. A framework for understanding the reaction pathway is presented. 相似文献
30.
Bilal Elhajjar Abdelkader Mojtabi Manuel Marcoux Marie-Catherine Charrier-Mojtabi 《Comptes Rendus Mecanique》2006,334(10):621-627
We propose an analytical and numerical study of the combined action of the thermodiffusion and the convection in a binary mixture. The combination of these two phenomena is called thermogravitational diffusion. We are interested in quantifying the separation in a horizontal parallelepipedic cavity filled with a binary mixture and subjected to a constant horizontal temperature gradient on the two horizontal walls, the other walls being thermally insulated and impermeable. This new procedure is different from the classical one where the cavity is vertical and differentially heated on the two vertical walls. To cite this article: B. Elhajjar et al., C. R. Mecanique 334 (2006). 相似文献