TY - JOUR
T1 - Triple quantum decoherence under multiple refocusing
T2 - Slow correlated chemical shift modulations of C′ and N nuclei in proteins
AU - Wist, Julien
AU - Frueh, Dominique
AU - Tolman, Joel R.
AU - Bodenhausen, Geoffrey
N1 - Funding Information:
We are indebted to Martial Rey for his invaluable technical assistance. This research was supported by the Fond National de la Recherche Scientifique and by the Commission pour la Technologie et l’Innovation.
PY - 2004/3
Y1 - 2004/3
N2 - 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.
AB - 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.
KW - Chemical shift modulations
KW - Correlated fluctuations
KW - Cross-correlations
KW - Protein backbone dynamics slow motions
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U2 - 10.1023/B:JNMR.0000013699.48099.38
DO - 10.1023/B:JNMR.0000013699.48099.38
M3 - Article
C2 - 14752259
AN - SCOPUS:1242317865
SN - 0925-2738
VL - 28
SP - 263
EP - 272
JO - Journal of Biomolecular NMR
JF - Journal of Biomolecular NMR
IS - 3
ER -