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Philippe Lesot - One of the best experts on this subject based on the ideXlab platform.
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integrated computational protocol for the analysis of quadrupolar splittings from natural abundance deuterium nmr spectra in chiral Oriented Media
ChemPhysChem, 2017Co-Authors: Armando Navarrovazquez, P Berdague, Philippe LesotAbstract:The front cover artwork is provided by Dr. Armando Navarro-Vazquez from the department of fundamental chemistry of the Universidade Federal de Pernambuco (Brazil) as well as Dr. Philippe Berdague and Dr. Philippe Lesot (DR CNRS), both from the Institut de Chimie Moleculaire et des Materiaux d'Orsay of the Universite de Paris-Sud/Paris-Saclay (France). Graphically inspired by the famous word game «Scrabble», the image illustrates, through selected keywords, the analytical potential of a hyphenated computational protocol for investigating (achiral, prochiral or chiral) organic molecules by combining deuterium NMR spectroscopy at natural abundance level and chiral Oriented systems, as described in their article. Read the full text of the article at 10.1002/cphc.201601423.
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correlation 2d nmr experiments involving both 13c and 2h isotopes in Oriented Media methodological developments and analytical applications
Magnetic Resonance in Chemistry, 2014Co-Authors: Philippe Lesot, Olivier Lafon, P BerdagueAbstract:Correlation 2D-NMR experiments for $^{13}$C and $^2H$ isotopes turn out to be powerful methods for the assignment of the quadrupolar doublets in the $^2$H NMR spectra of isotopically modified (polydeuterated or perdeuterated) or unmodified solutes in homogeneously Oriented solvents, such as thermotropic systems or lyotropic liquid crystals. We review here the different pulse sequences, which have been employed, their properties, and their most salient applications. These 2D-NMR sequences have been used for (i) $^{13}$C$_2$-$^2$H correlation with and without $^1$H relay and (ii) $^2$H–$^2$H correlation with $^{13}$C relay. The $^{13}$C$_2$-$^2$H correlation experiments without $^1$H relay have been achieved for specifically deuterated or non-selectively deuterated analytes, but also more recently for isotopically unmodified ones thanks to the high sensitivity of very high-field NMR spectrometers (21.1 T) equipped with cryogenic probes. The $^{13}$C$_2$-$^2$H correlation 2D-NMR experiments are especially useful for the assignment of overcrowded deuterium spectra because the $^2$H signals are correlated to $^{13}$C signals, which benefit from a much larger dispersion of chemical shifts. In this contribution, particular attention will be paid to the use of correlation 2D-NMR experiments for $^2$H and $^{13}$C nuclei in weakly aligning, polypeptide Oriented chiral solvents, because these methods are useful and original tools for enantiomeric and enantiotopic analyses.
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on the fly kinetics of enzymatic racemization using deuterium nmr in dna based chiral Oriented Media
Analytical Chemistry, 2013Co-Authors: Monique Chanhuot, Philippe Lesot, Philippe Pelupessy, Luminita Duma, Geoffrey Bodenhausen, Patricia Duchambon, Michael D ToneyAbstract:We report the in situ and real-time monitoring of the interconversion of L- and D-alanine-d(3) by alanine racemase from Bacillus stearothermophilus directly observed by H-2 NMR spectroscopy in anisotropic phase. The enantiomers are distinguished by the difference of their H-2 quadrupolar splittings in a chiral liquid crystal containing short DNA fragments. The proof-of-principle, the reliability, and the robustness of this new method is demonstrated by the determination of the turnover rates of the enzyme using the Michaelis Menten model.
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investigation of fatty acid elongation and desaturation steps in fusarium lateritium by quantitative two dimensional deuterium nmr spectroscopy in chiral Oriented Media
Journal of Biological Chemistry, 2009Co-Authors: Vincent Baillif, Philippe Lesot, Richard J Robins, Steven Le Feunteun, Isabelle BillaultAbstract:The origin of hydrogen atoms during fatty acid biosynthesis in Fusarium lateritium has been quantified by isotope tracking close to natural abundance. Methyl linoleate was isolated from F. lateritium grown in natural abundance medium or in medium slightly enriched with labeled water, glucose, or acetate, and the 2H incorporation was determined by quantitative 2H-{1H} NMR in isotropic and chiral Oriented solvents. Thus, the individual (2H/1H)i ratio at each pro-R and pro-S hydrogen position of the CH2 groups along the chain can be analyzed. These values allow the isotope redistribution coefficients (aij) that characterize the specific source of each hydrogen atom to be related to the nonexchangeable hydrogen atoms in glucose and to the medium water. In turn, these can be related to the stereoselectivity that operates during the introduction or removal of hydrogens along the fatty acid chain. First, at even CH2 the pro-S hydrogen comes only from water by protonation, whereas the pro-R hydrogen is introduced partly via acetate but principally from water. Second, the nonexchangeable hydrogens of glucose (positions H-6,6 and H-1) are shown to be introduced to the odd CH2 via the NAD(P)H pool used by both reductases involved in the elongation steps of the fatty acid chain. Third, it is proved that hydrogens removed at sites 9,10 and 12,13 during desaturation by Δ9- and Δ12-desaturases are pro-R, and that during these desaturation steps α-secondary kinetic isotope effects occur at the 9 and 12 positions and not at the 10 and 13 positions.
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nmr experimental evidence of the differentiation of enantiotopic directions in cs and c2v molecules using partially Oriented chiral Media
Journal of the American Chemical Society, 2001Co-Authors: Christie Aroulanda, Denis Merlet, Jacques Courtieu, Philippe LesotAbstract:We report new and explicit experimental evidence of the differentiation of 1H−1H, 13C−1H, and 13C−2H enantiotopic directions in prochiral molecules with Cs and C2v symmetry dissolved in a chiral liquid-crystalline phase using 13C and 2H-{1H} NMR spectroscopy at the natural abundance level. The case of endo-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, bicyclo[2.2.1]hepta-2,5-diene, and ethyl alcohol Oriented in organic solutions of poly-γ-benzyl-l-glutamate (PBLG) or poly-e-carbobenzyloxy-l-lysine (PCBLL) is investigated and discussed. Next, we describe the first NMR differentiation of enantiotopic directions in a C2v molecule with no prostereogenic carbon using malononitrile as a model. The various results presented in this work experimentally validate our recent theoretical arguments which predict that NMR spectra of nonplanar Cs and C2v compounds embedded in a chiral Oriented solvent should differ from those recorded in nonchiral Oriented Media, because their effective molecular symmetry point gr...
J R Tolman - One of the best experts on this subject based on the ideXlab platform.
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a novel approach to the retrieval of structural and dynamic information from residual dipolar couplings using several Oriented Media in biomolecular nmr spectroscopy
Journal of the American Chemical Society, 2002Co-Authors: J R TolmanAbstract:The interpretation of residual dipolar couplings in terms of molecular properties of interest is complicated because of difficulties in separating structural and dynamic effects as well as the need to estimate alignment tensor parameters a priori. An approach is introduced here that allows many of these difficulties to be circumvented when data are acquired in multiple alignment Media. The method allows the simultaneous extraction of both structural and dynamic information directly from the residual dipolar coupling data, in favorable cases even in the complete absence of prior structural knowledge. Application to the protein ubiquitin indicates greater amplitudes of internal motion than expected from traditional 15N spin relaxation analysis.
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nmr structures of biomolecules using field Oriented Media and residual dipolar couplings
Quarterly Reviews of Biophysics, 2000Co-Authors: James H Prestegard, Hashim M Alhashimi, J R TolmanAbstract:2. Theoretical treatment of dipolar interactions 376 2.1 Anisotropic interactions as probes of macromolecular structure and dynamics 376 2.1.1 The dipolar interaction 376 2.1.2 Averaging in the solution state 377 2.2 Ordering of a rigid body 377 2.2.1 The Saupe order tensor 378 2.2.2 Orientational probability distribution function 380 2.2.3 The generalized degree of order 380 2.3 Molecular structure and internal dynamics 381
Monique Chanhuot - One of the best experts on this subject based on the ideXlab platform.
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on the fly kinetics of enzymatic racemization using deuterium nmr in dna based chiral Oriented Media
Analytical Chemistry, 2013Co-Authors: Monique Chanhuot, Philippe Lesot, Philippe Pelupessy, Luminita Duma, Geoffrey Bodenhausen, Patricia Duchambon, Michael D ToneyAbstract:We report the in situ and real-time monitoring of the interconversion of L- and D-alanine-d(3) by alanine racemase from Bacillus stearothermophilus directly observed by H-2 NMR spectroscopy in anisotropic phase. The enantiomers are distinguished by the difference of their H-2 quadrupolar splittings in a chiral liquid crystal containing short DNA fragments. The proof-of-principle, the reliability, and the robustness of this new method is demonstrated by the determination of the turnover rates of the enzyme using the Michaelis Menten model.
Amy Bleakley - One of the best experts on this subject based on the ideXlab platform.
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adolescent perceptions of black Oriented Media the day beyonce turned black can black Oriented films and tv programs be marketed more broadly
Journal of Advertising Research, 2019Co-Authors: Morgan E Ellithorpe, Michael Hennessy, Amy BleakleyAbstract:ABSTRACT Black-Oriented Media, content with predominantly Black casts or racial themes, is marketed primarily toward Black audiences, but how audiences perceive such targeting is unclear. Black and White adolescents ( N = 1,990) identified the perceived target audience of 15 movies, 12 of them Black Oriented. Results suggest that Black adolescents, especially those with strong ethnic identity, differentiate Black-Oriented films from mainstream movies. Black adolescents reported higher exposure to Black-Oriented films, particularly if they perceived such films as targeted to Black audiences. White adolescents found it more difficult to identify Black-Oriented films. Black-Oriented films therefore might be marketed successfully beyond Black audiences.
Armando Navarrovazquez - One of the best experts on this subject based on the ideXlab platform.
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integrated computational protocol for the analysis of quadrupolar splittings from natural abundance deuterium nmr spectra in chiral Oriented Media
ChemPhysChem, 2017Co-Authors: Armando Navarrovazquez, P Berdague, Philippe LesotAbstract:The front cover artwork is provided by Dr. Armando Navarro-Vazquez from the department of fundamental chemistry of the Universidade Federal de Pernambuco (Brazil) as well as Dr. Philippe Berdague and Dr. Philippe Lesot (DR CNRS), both from the Institut de Chimie Moleculaire et des Materiaux d'Orsay of the Universite de Paris-Sud/Paris-Saclay (France). Graphically inspired by the famous word game «Scrabble», the image illustrates, through selected keywords, the analytical potential of a hyphenated computational protocol for investigating (achiral, prochiral or chiral) organic molecules by combining deuterium NMR spectroscopy at natural abundance level and chiral Oriented systems, as described in their article. Read the full text of the article at 10.1002/cphc.201601423.