Influence of cross-correlation between the chemical shift anisotropies of pairs of nuclei on multiple-quantum relaxation rates in macromolecules

The relaxation of multiple-quantum coherence due to intramolecular dipole-dipole and chemical shift anisotropy (CSA) relaxation mechanisms is described. It is shown that cross-correlation between the CSAs of the active spins can affect the relaxation of H-1-N-15 two-spin coherences in the protein backbone. An experiment that enables this effect to be monitored is discussed. Data are presented for perdeuterated N-15-labelled human dynamic light chain 1 protein (hdlc1). An analysis of the results yields a value for the CSA of the active H-1. (C) 1999 Elsevier Science B.V. All rights reserved.