Relaxation of two-spin coherence due to cross-correlated fluctuations of dipole-dipole couplings and anisotropic shifts in NMR of N-15,C-13-labeled biomolecules
E. Chiarparin et al., Relaxation of two-spin coherence due to cross-correlated fluctuations of dipole-dipole couplings and anisotropic shifts in NMR of N-15,C-13-labeled biomolecules, J AM CHEM S, 121(29), 1999, pp. 6876-6883
A comprehensive description is presented of the effects on two-spin coheren
ces (i.e., superpositions of zero- and double-quantum coherences) of cross-
correlation between the fluctuations of two different relaxation mechanisms
in nuclear magnetic resonance (NMR). Dipole-dipole (DD) interactions betwe
en four nuclei and chemical shift anisotropy (CSA) of two of these nuclei a
re considered. Two complementary experiments have been designed for N-15,C-
13-labeled proteins to quantify the effects of cross-correlation between th
e Ca-13(alpha)-(1)Ha(alpha) and N-15-H-1(N) dipolar interactions on two-spi
n coherences involving C-13(alpha) of the ith residue with the N-15 Of the
(i+1)th amino acid. Two other experiments allow one to quantify the effect
of cross-correlation between the C-13' (carbonyl) CSA and the (Calpha-1Halp
ha)-C-13 dipolar coupling on the relaxation of two-spin coherences involvin
g the C-13' and C-13(alpha) nuclei on the same residue of the protein. Thes
e experiments have been used to extract relevant cross-correlation rates in
N-15,C-13-labeled human ubiquitin. These rates show a high degree of corre
lation with the backbone Psi angles in proteins.