排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
Joachim GarricJean-Michel Léger Axelle GrelardMasakazu Ohkita Ivan Huc 《Tetrahedron letters》2003,44(7):1421-1424
X-Ray crystallography and NMR show a strong preference for trans conformers of N′-phenyl or N′-(2-pyridyl) 2-pyridinecarboxylic acid hydrazides, stabilized by an NHNpyr. intramolecular hydrogen bond both in the solid state and in solution. This allows us to extrapolate that oligomers of this unit should adopt extended linear conformations. 相似文献
2.
δ-Azaproline, a new bis-nitrogen proline surrogate has been used in order to control the conformation of an AA–ΨPro bond. Conformational analysis of Xaa1–δ-azaPro–Xaa3 performed by NMR, IR experiments, and molecular modeling revealed a preference for a trans conformation of the Xaa1–δ-azaPro bond when δ-azaPro is protected by a Boc group. The removal of the Boc protection leads to the establishment of a C10 pseudocycle via a hydrogen bond network favoring the cis conformation of the Xaa1–δ-azaPro bond. 相似文献
3.
Back Cover: Assessment of DNA Binding to Human Rad51 Protein by using Quartz Crystal Microbalance and Atomic Force Microscopy: Effects of ADP and BRC4‐28 Peptide Inhibitor (ChemPhysChem 17/2014) 下载免费PDF全文
4.
Dautrey Sébastien Bodiguel Jacques Arrault Axelle Jamart-Grégoire Brigitte 《Tetrahedron》2012,68(23):4362-4367
1H NMR and FTIR experiments performed on the 1:1[α:α-N-amino]mers series let us to point out a rare NH–π interaction between the carbamidic NH of the i residue and the phenyl group of a phenylalanine residue located at i+2. 相似文献
5.
1D NMR Homodecoupled 1H Spectra with Scalar Coupling Constants from 2D NemoZS‐DIAG Experiments 下载免费PDF全文
Axelle Cotte Dr. Damien Jeannerat 《Angewandte Chemie (International ed. in English)》2015,54(20):6016-6018
A two‐dimensional liquid‐state NMR experiment cleanly separating chemical shifts and scalar couplings information is introduced. This DIAG experiment takes advantage of a drastic reduction of the spectral window in the indirect dimension to be quickly recorded and of a new non‐equidistant modulation of the selective pulse to improve the sensitivity of the broadband homodecoupling Zangger–Sterk sequence element by one order of magnitude. A simple automatic analysis results in 1D spectra displaying singlets and lists of the scalar couplings for first‐order multiplets. This facilitates the analysis of 1D spectra by resolving multiplets based on their differences in chemical shifts and coupling structures. 相似文献
6.
The determination of seven arsenic species in seafood was performed using ion exchange chromatography on an IonPac AS7 column with inductively coupled plasma mass spectrometry detection after microwave assisted extraction. The effect of five parameters on arsenic extraction recoveries was evaluated in certified reference materials. The recoveries of total arsenic and of arsenic species with the two best extraction media (100% H2O and 80% aqueous MeOH) were generally similar in the five seafood certified reference materials considered. However, because MeOH co-elutes with arsenite, which would result in a positively biased arsenite concentration, the 100% H2O extraction conditions were selected for validation of the method. Figures of merit (linearity, LOQs (0.019-0.075 mg As kg−1), specificity, trueness (with recoveries between 82% (As(III)) and 104% (As(V) based on spikes or certified concentrations), repeatability (3-14%), and intermediate precision reproducibility (9-16%) of the proposed method were satisfactory for the determination of arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenate, arsenobetaine and arsenocholine in fish and shellfish. The performance criteria for trimethylarsine oxide, however, were less satisfactory. The method was then applied to 65 different seafood samples. Arsenobetaine was the main species in all samples. The percentage of inorganic arsenic varied between 0.4-15.8% in shellfish and 0.5-1.9% at the utmost in fish. The main advantage of this method that uses only H2O as an extractant and nitric acid as gradient eluent is its great compatibility with the long-term stability of both IEC separation and ICP-MS detection. 相似文献
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8.
Leufroy A Noël L Beauchemin D Guérin T 《Analytical and bioanalytical chemistry》2012,402(9):2849-2859
A continuous leaching method coupled online with inductively coupled plasma mass spectrometry (ICP-MS) detection was used
to assess the maximum bioaccessibility of arsenic (As) in seafood samples. The method simulates continuous-flow digestion
by successively pumping artificial saliva, gastric and intestinal juices through a mini-column of powdered sample directly
connected to the nebuliser of an ICP-MS instrument. The method allows the real-time measurement of As being released by a
given reagent. Because the analyte is continuously removed from the system, in contrast to batch methods, the dissolution
equilibrium is driven to the right, hence quickly providing information about the worst-case scenario. Following consecutive
leaching by the digestive reagents, the leachates were subject to speciation analysis by ion-exchange chromatography with
ICP-MS detection to determine the arsenic species released. Finally, the remaining residue from the mini-column was fully
digested to verify mass balance. The method was used to determine the bioaccessibility of total As and As species in four
certified reference materials and in several real seafood samples. The mass balance was verified in each case. Generally speaking,
the non-toxic form was easily released whereas the inorganic forms were poorly bioaccessible. 相似文献
9.
We present several applications of both wide-line and magic angle spinning (MAS) solid-state NMR of bicelles in which are embedded fragments of a tyrosine kinase receptor or enkephalins. The magnetically orientable bicelle membranes are shown to be of particular interest for studying the functional properties of lipids and proteins in a state that is very close to their natural environment. Quadrupolar, dipolar and chemical shielding interactions can be used to determine minute alterations of internal membrane dynamics and the orientation of peptides with respect to the membrane plane. MAS of bicelles can in turn lead to high-resolution proton spectra of hydrated membranes. Using deuterium-proton contrast methods one can then obtain pseudo-high-resolution proton spectra of peptides or proteins embedded in deuterated membranes and determine their atomic 3D structure using quasi-conventional liquid-state NMR methods. 相似文献
10.
Maxime Pedeutour Axelle ArraultMarie-Christine Averlant-Petit Brigitte Jamart-Grégoire 《Tetrahedron letters》2014
In order to investigate the ability of self-organization of the alternance of α-amino and α-N-amino-acids the synthesis of cyclo 1:1-[α/α-N-amino]mers has been achieved by an iterative sequence of deprotection and coupling reactions followed by a macrocyclization step. The self-assembling of N-amino deprotected cyclo-oligomers has been characterized using X-ray diffraction experiments and FT-IR analysis. 相似文献