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D Merlet

Publications and source records attributed to D Merlet.

13 recordsLinked to original sources
PubMed2006

Visualisation of enantiomers via insertion of a BIRD module in X-H correlation experiments in chiral liquid crystal solvent.

Several 13C-1H NMR techniques are derived simplifying the visualisation of enantiomers in chiral ordering solvents. They proceed through various heteronuclear 2D experiments where a bilinear rotation decoupling sequence (BIRD) is inserted in the middle of the t1 evolution period. In this way, the small couplings are refocused while the large couplings are preserved. The methods allow extracting precise values of one-bond carbon-proton residual dipolar couplings for each enantiomer out of unresolved proton-coupled 13C or carbon-coupled 1H spectra. Illustrative examples are analysed and discussed using various pulse sequences.

Algorithms↗
PubMed2006

An investigation of the structure and bond rotational potential of some fluorinated ethanes by NMR spectroscopy of solutions in nematic liquid crystalline solvents.

NMR spectra of 1,2-dibromo-1,1-difluoroethane and 1-bromo-2-iodo-tetrafluoroethane dissolved in nematic liquid crystalline solvents have been analysed to yield the magnitudes and signs of the scalar couplings, J(ij), and total anisotropic couplings, T(ij), between all the (1)H, (19)F, and (13)C nuclei, except for those between two (13)C nuclei. The values obtained for T(ij) in principle contain a contribution from J(ij)(aniso), the component along the static applied magnetic field of the anisotropic part of the electron-mediated spin-spin coupling. Neglecting this contribution allows partially averaged dipolar couplings, D(ij), to be extracted from the T(ij), and these were used to determine the structure, orientational order, and the conformational distribution generated by rotation about the C-C bond. The values obtained are compared with the results of calculations by ab initio and density functional methods. The differences found are no greater than those obtained for similar compounds which do not contain fluorine, so that there is no definitive evidence for significant contributions from J(CF)(aniso) or J(FF)(aniso) in the two compounds studied.

Journal Article↗
PubMed2005

Obtaining the structure and bond rotational potential of a substituted ethane by NMR spectroscopy of solutions in nematic liquid-crystalline solvents.

Partially averaged dipolar couplings (also referred to as residual dipolar couplings) D(ij) can be obtained from the analysis of the NMR spectra of molecules dissolved in liquid-crystalline solvents. Their values for a nonrigid molecule depend upon the bond lengths and angles, the rotational potentials, and the orientational order of the molecules. The molecule studied, 1-chloro-2-bromoethane, is one of the simplest example of a substituted alkane in which the rotational potential has three minimum-energy positions, trans and gauche+/-conformations, and the present investigation explores the problems inherent in deriving the form of the potential and the molecular geometry from the set of partially averaged couplings between the protons, and between protons and (13)C nuclei. The geometrical parameters and the rotational potential obtained are compared with the results from a density-functional theory method.

Journal Article↗
PubMed2002

Selective detection of the proton NMR spectra of molecules containing rare spins at natural abundance in liquid crystalline samples.

It is shown that the proton NMR spectra of molecules containing rare spins at natural abundance dissolved in a liquid crystalline solvent can be obtained free from the strong lines from the spectrum of the abundant isotopomer by the 2D HSQC NMR experiment. The technique can also give the individual chemical shifts of the rare spins, and, for a molecule containing another abundant nucleus, such as fluorine, the rare spin--(19)F total anisotropic couplings are also obtained. The usefulness of the technique is demonstrated for molecules containing (13)C as the rare spins.

Journal Article↗
PubMed2001

NMR experimental evidence of the differentiation of enantiotopic directions in C(s) and C(2v) molecules using partially oriented, chiral media.

We report new and explicit experimental evidence of the differentiation of (1)H-(1)H, (13)C-(1)H, and (13)C-(2)H enantiotopic directions in prochiral molecules with C(s) and C(2v)symmetry dissolved in a chiral liquid-crystalline phase using (13)C and (2)H-[(1)H] 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-gamma-benzyl-L-glutamate (PBLG) or poly-epsilon-carbobenzyloxy-L-lysine (PCBLL) is investigated and discussed. Next, we describe the first NMR differentiation of enantiotopic directions in a C(2v) 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 C(s) and C(2v) compounds embedded in a chiral oriented solvent should differ from those recorded in nonchiral oriented media, because their effective molecular symmetry point group (interacting molecule) is different from their molecular point group (isolated molecule). In addition, the differentiation of enantiotopic directions in C(2v) molecules exhibiting no prostereogenic tetrahedral center illustrates for the first time an old stereochemical hypothesis which speculates that "for molecules of the type CXXYY. the two X groups as well as the Y groups are equivalent and cannot be distinguished in chiral or achiral circumstances. However, the relationships between X and Y groups are not all equivalent. The four X-Y relationships may be ordered into two enantiotopic sets of two equivalent relationships" (Mislow, K.; Raban, M. Top. Stereochem. 1967, 1, 1) and validate the stereogenicity concepts proposed more recently by Fujita (Fujita, S. J. Am. Chem. Soc. 1990, 112, 3390).

Journal Article↗
PubMed2000

Soil solutions and surface water analysis in two contrasted watersheds impacted by acid deposition, Vosges mountains, N.E. France: interpretation in terms of Al impact and nutrient imbalance.

Two acid watersheds in the Vosges mountains (N.E. France), one with a podzol, the other with an acid brown soil, were monitored by analysing soil solutions and two related springs for total chemistry and Al speciation. High concentrations of inorganic Al did not occur in the podzol upper horizons but were evident in the corresponding spring, together with low concentrations of Ca. In the acid brown soil area, high concentrations of inorganic Al occurred in the leaching water draining the upper soil horizons, but not in the undrained water nor in the spring, the latter exhibiting rather high Ca content. In both watersheds, needle yellowing in conifers could be observed and might be ascribed to Mg deficiency rather than to Al toxicity.

Acids↗
PubMed1990

[Isolation of tubular proximal cells of the human kidney by affinity chromatography using Lotus tetragonolobus lectin].

An affinity chromatography technique, using a lectin issued from Lotus tetragonolobus as ligand, and coupled to Sepharose 6MB support, has been chosen to enrich a cellular population in tubular proximal cells. Cell desorption was obtained with a competitive sugar, L Fucose. Intensive enzymatic brush border activity, shown in selected cells compared with initial cellular mixture, evidenced an enrichment in proximal tubular cells. These results prove that lectin use as ligand in affinity chromatography permits the separation of renal cell populations and presents the advantage that the bound cells can be recovered by a gentle competitive elution for further cultures.

Cell Separation↗
PubMed1989

[Morphologic and enzymatic characteristics of healthy human kidney epithelial tubular cells in culture].

The present study defines morphological and enzymatic characteristics of human healthy renal tubular cells in primary culture, and during three passages. The results confirm the ability to culture human renal tubular cells and to quantitatively evaluate the activity of specific tubular enzymes in the cells and in the culture medium. Such determinations can be compared to similar enzyme activity research in renal biopsies or in urines, to investigate human renal cell functions, in clinical, pharmacological or toxicological approaches.

Alkaline Phosphatase↗
PubMed1989

[Effect of cisplatin on healthy human renal tubular cells and cancerous cells in culture].

An in vitro comparative cis-platin cytotoxicity was evidenced in human renal normal and tumoral cultured cells. Cytotoxic effect was estimated at membrane level by intracellular enzymatic markers release into culture medium and nuclear level by ADN synthesis inhibition after 3H thymidine incorporation. These results show a more intensive activity of cis-platin in normal tubular cells than in tumoral ones.

Cells, Cultured↗
PubMedDate not supplied

[Methods of in vitro evaluation for nephrotoxicity].

Mechanisms and precise targets of nephrotoxicants have been evidenced in experimental animals, a very important contribution for decades. But, structural and functional heterogeneity in renal tissue makes often difficult the exact determination of the molecular targets at renal cell level. Indeed, some new in vitro models have been gradually reported. This non exhaustive review purposes to present the different recent models, ever more reductionist, as isolated kidneys, kidney slices, isolated renal cells or renal cultured cells to assess the nephrotoxicity of new molecules. For every model are presented a brief history, the principle of the technique, viability criteria and its relative interest for renal toxicology. In conclusion, a general discussion points out the main advantages and limits of each one.

Animals↗