Principles and applications of cross-correlated relaxation in biomolecules

In liquid-state NMR, spin relaxation due to cross-correlation of two anisot ropic spin interactions can provide useful information about molecular stru cture and dynamics. These effects are manifest as differential line widths or line intensities in the NMR spectra. Recently, new experiments were deve loped for the accurate measurement of numerous cross-correlated relaxation rates in scalar coupled multi-spin systems. The recently introduced concept of transverse relaxation optimized spectroscopy (TROSY) is also based on c ross-correlated relaxation. The present article outlines the basic concepts and experimental techniques necessary for understanding and exploiting cro ss-correlated relaxation effects in macromolecules. In addition, representa tive examples illustrate the potential of cross-correlated relaxation for h igh resolution NMR studies of proteins and nucleic acids. (C) 2000 John Wil ey & Sons. Inc.