P. Pelupessy et al., Efficient determination of angles subtended by C-alpha-H-alpha and N-H-N vectors in proteins via dipole-dipole cross-correlation, J BIOM NMR, 13(4), 1999, pp. 375-380
The angle Theta(C alpha H alpha,NHN) subtended by the internuclear vectors
C-13(alpha)-H-alpha and N-15-H-N in doubly-labeled proteins can be determin
ed by observing the effect of cross-correlation between the dipolar interac
tions on zero- and double-quantum coherences involving C-13(alpha) and N-15
. Two complementary 2D experiments with the appearance of N-15-H-N correlat
ion spectra yield signal intensities that depend on the rate of interconver
sion through cross-correlated relaxation of in-phase and doubly antiphase z
ero- and double-quantum coherences. The ratio of the signal intensities in
the two experiments bears a simple relationship to the cross-correlation ra
te, and hence to the angle Theta(C alpha H alpha,NHN). Assuming planarity o
f the peptide bond, the dihedral angle Psi (between C-alpha and C') can be
determined from the knowledge of Theta(C alpha H alpha,NHN). The experiment
s are very time-effective and provide good sensitivity and excellent spectr
al resolution.