Nicole Goasdoue

Degradation of algal (Ascophyllum nodosum) fucoidan by an enzymatic activity contained in digestive glands of the marine mollusc Pecten maximus

Abstract A protein extract from digestive glands of the marine mollusc Pecten maximus was shown to possess fucoidan-degrading activity. This activity was able to release l -fucose from fucoidan derived from the brown algae Ascophyllum nodosum, and markedly reduce the molecular size of the polysaccharide. An enzymatically degraded fucoidan was produced and analysed by NMR spectroscopy. The 2D 1H NMR data obtained for the first time on low-molecular-weight fractions of algal fucoidan provided new insight into the structure of the polysaccharide. The latter has a randomly organised structure, involving (1→3)- and (1→4)-linked unsulfated and 2-sulfated-α- l -fucose residues.

Sur les zinciques issus des α-bromonitriles : I. Préparation, structure et réactivité avec les aldéhydes, les cétones et les alcoylidènes malonates d'éthyle

Abstract Organozinc compounds derived from α-bromonitriles are readily prepared in solution in tetrahydrofuran (THF) and exist in the C metallated form. They condense normally with aldehydes and saturated ketones. A number of new β-hydroxy-nitriles are described. The addition of conjugated unsaturated ketones results in the formation of β-hydroxynitriles or ketonitriles, depending on the nature of the initial bromonitrile. The stereochemistry of the reaction of benzaldehyde with zinc-α-bromonitrile is not influenced by the nature of the solvent. Condensation with diethyl-malonate alkylidenes lead to the expected 1,4-addition products.

Non-aqueous capillary electrophoresis of the positional isomers of a sulfated monosaccharide

A non-aqueous capillary electrophoresis (NACE) method coupled to indirect absorbance detection has been developed for the separation of the three positional isomers of monosulfated fucose. The optimized electrolyte was composed of 12 mM ethanolamine, 2 mM trimesic acid buffer in a methanol-ethanol (1:1, v/v) mixture. As the retained electrolyte entails no separating agent other than the pH buffer, the NACE separation of the positional isomers has been ascribed mainly to selective ion-pairing with the electrolyte counter-ion and the possibility of a selective solvation effect in the alcohol mixture. In the absence of pure isomeric standards, peak identification was completed by MS and NMR spectroscopy and selective enzymatic desulfation. This method should be of interest for the structure elucidation of monosulfated fucose-based polysaccharides and for the screening of sulfoesterase of unknown activity.

Prolinoamino Acids as Tools to Build Bifunctionalized, Stable β-Turns in Water

Keywords: beta-turn ; bioorganic chemistry ; NMR spectroscopy ; peptidomimetics ; prolinoamino acid ; Ultraviolet Circular-Dichroism ; Side-Chain Contribution ; Asymmetric-Synthesis ; Amino-Acids ; Conformation ; Constraints ; Derivatives ; Peptides ; Ligands ; Analogs Reference EPFL-ARTICLE-149200doi:10.1002/cbic.200900572 Record created on 2010-06-03, modified on 2017-05-12

Sur les zinciques issus des α-bromonitriles : II. Réactivité avec les anhydrides d'acides

Abstract The condensation of organozinc compounds derived from α-bromonitriles with acid anhydrides results in two different types of compounds: either β-ketonitriles or cis and trans enol esters according to the nature of the initial bromonitrile. Various factors which affect this reaction are being studied. A method of preparation for the above mentioned products is advanced.

Sur les organozinciques issus des α-bromonitriles : III. Reactivite vis-a-vis des nitriles

Abstract The condensation of organozinc compounds with nitriles gives either β-ketonitriles or ketenaminonitriles , according to the method used. When the starting nitrile is aromatic, and also in the case of α-bromoisobutyronitrile a nitrogen compound was observed similar to a β-lactimine nitrile.