Analysis of NAD 2D-NMR Spectra of Saturated Fatty Acids in Polypeptide Aligning Media by Experimental and Modeling Approaches

Authors

  • Zeinab Serhan,

    1. RMN en Milieu Orienté, ICMMO, UMR-CNRS 8182, Université de Paris Sud 11, 91405 Orsay Cedex (France)
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  • Andrea Borgogno,

    1. Università di Padova, Dipartimento di Scienze Chimiche, Via Marzolo, 1, 35131 Padova (Italy)
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  • Dr. Isabelle Billault,

    1. RMN en Milieu Orienté, ICMMO, UMR-CNRS 8182, Université de Paris Sud 11, 91405 Orsay Cedex (France)
    2. Université de Nantes, Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR CNRS 6230, CNRS UMR 6006, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex (France)
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  • Dr. Alberta Ferrarini,

    Corresponding author
    1. Università di Padova, Dipartimento di Scienze Chimiche, Via Marzolo, 1, 35131 Padova (Italy)
    • Università di Padova, Dipartimento di Scienze Chimiche, Via Marzolo, 1, 35131 Padova (Italy)
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  • Dr. Philippe Lesot

    Corresponding author
    1. RMN en Milieu Orienté, ICMMO, UMR-CNRS 8182, Université de Paris Sud 11, 91405 Orsay Cedex (France)
    • RMN en Milieu Orienté, ICMMO, UMR-CNRS 8182, Université de Paris Sud 11, 91405 Orsay Cedex (France)
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Abstract

The overall and detailed elucidation (including the stereochemical aspects) of enzymatic mechanisms requires the access to all reliable information related to the natural isotopic fractionation of both precursors and products. Natural abundance deuterium (NAD) 2D-NMR experiments in polypeptide liquid-crystalline solutions are a new, suitable tool for analyzing site-specific deuterium isotopic distribution profiles. Here this method is utilized for analyzing saturated C14 to C18 fatty acid methyl esters (FAMEs), which are challenging because of the crowding of signals in a narrow spectral region. Experiments in achiral and chiral oriented solutions were performed. The spectral analysis is supplemented by the theoretical prediction of quadrupolar splittings as a function of the geometry and flexibility of FAMEs, based on a novel computational methodology. This allows us to confirm the spectral assignments, while providing insights into the mechanism of solute ordering in liquid-crystalline polypeptide solutions. This is found to be dominated by steric repulsions between FAMEs and polypeptides.

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