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Journal Articles Communications Chemistry Year : 2018

Dipolar couplings in solid polypeptides probed by 14N NMR spectroscopy

Abstract

The acquisition of 14N NMR spectra in solid samples is challenging due to quadrupolar couplings with magnitudes up to several MHz. This nucleus is nonetheless important as it is involved in the formation of essential secondary structures in biological systems. Here we report the structural study of the atomic environment of amide functions in polypeptides using magic-angle spinning NMR spectroscopy of the ubiquitous 14N isotope. The cyclic undecapeptide cyclosporin, in which only four hydrogen atoms are directly bound to nitrogen atoms, is chosen for illustration. Structural details of different environments can be revealed without resorting to isotopic enrichment. The network of inter- and intra-residue dipolar couplings between amide 14N nuclei and nearby protons can be probed and mapped out up to a tunable cutoff distance. Density functional theory calculations of NMR quadrupolar interaction tensors agree well with the experimental evidence and allow the unambiguous assignment of all four non-methylated NH nitrogen sites and neighboring proton nuclei.
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Dates and versions

hal-02285948 , version 1 (13-09-2019)

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Diego Carnevale, Benoit Grosjean, Geoffrey Bodenhausen. Dipolar couplings in solid polypeptides probed by 14N NMR spectroscopy. Communications Chemistry, 2018, 1 (1), ⟨10.1038/s42004-018-0072-5⟩. ⟨hal-02285948⟩
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