Triple quantum decoherence under multiple refocusing: Slow correlated chemical shift modulations of C′ and N nuclei in proteins

Julien Wist, Dominique Frueh, Joel R. Tolman, Geoffrey Bodenhausen

Research output: Contribution to journalArticle

Abstract

A new experiment allows the identification of residues that feature slow conformational exchange in macromolecules. Rotations about dihedral angles that are slower than the global correlation time τc cause a modulation of the isotropic chemical shifts of the nuclei. If these fluctuations are correlated they induce a differential line broadening between three-spin single-quantum and triple-quantum coherences involving three nuclei such as the carbonyl C′, the neighbouring amide nitrogen N and the amide proton HN belonging to a pair of consecutive amino acids. A cross-corelated relaxation rate RC′NCS/CS can be determined that corresponds to the sum of the isotropic and anisotropic contributions to the chemical shift modulations of the carbonyl carbon and nitrogen nuclei. Only the isotropic contributions depend on the pulse repetition rate of a multiple-refocusing sequence. An attenuation of the relaxation rate with increasing pulse repetition rate can therefore be attributed to slow motions. The asparagine N25 residue of ubiquitin, located in the first α-helix, is shown to feature significant slow conformational exchange.

Original languageEnglish (US)
Pages (from-to)263-272
Number of pages10
JournalJournal of Biomolecular NMR
Volume28
Issue number3
DOIs
StatePublished - Mar 1 2004
Externally publishedYes

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Keywords

  • Chemical shift modulations
  • Correlated fluctuations
  • Cross-correlations
  • Protein backbone dynamics slow motions

ASJC Scopus subject areas

  • Biochemistry
  • Spectroscopy

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