Cross-correlation between a carbonyl C' chemical shift anisotropy and a long-range dipolar C'HA coupling in proteins using symmetrical reconversion.

A new sequence is described to measure the cross-correlation rates between the chemical shift anisotropy of the carbonyl carbon-13 nucleus and the dipole-dipole interaction between this carbonyl and the alpha-proton in proteins. The sequence is based on the symmetrical reconversion principle and is insensitive to experimental errors and to violations of the secular approximation. The cross-correlation rate depends on the backbone angle psi. The advantages and limitations of the sequence are discussed.