The effects of cross-correlation between Curie spin-nuclear dinances are not normally observed in high-resolution spectra. pole and nuclear dipole-nuclear dipole interactions on the line-The reason for this is that processes such as molecular tumwidths and resonance frequencies of the individual lines of an bling, which occur on a time scale faster than the inverse of AX multiplet in paramagnetic systems have been calculated. The the dipolar coupling constant, reduce its contribution through implication of the relaxation-induced frequency shift of the lines dynamic averaging. Most diamagnetic molecules interact (dynamic frequency shift) for the accurate measurement of residwith the applied magnetic field in a nearly orientation-indeual dipolar couplings in field-oriented systems has been discussed.
pendent manner and space is sampled isotropically, causing
Our simulations indicate that these effects may play a role in the average dipolar interaction to be zero. However, the the precise measurement of residual dipolar couplings in systems situation can be quite different in a paramagnetic molecule which belong to the small and intermediate tumbling regime, i.e., correlation times less than 5 ns. ᭧ 1997 Academic Press such as myoglobin, which has a paramagnetic susceptibility Key Words: dynamic frequency shift; paramagnetic relaxation; tensor that is highly anisotropic (Dx axial Å 2198 1 10 012 Curie spin relaxation; dipolar coupling; cross-correlation.
m 3 /mol, Dx rhombic Å 0573 1 10 012 m 3 /mol) (3). In cases such as this, the molecule has a preferred orientation in the applied magnetic field, and the effects of the dipolar cou-