We present two new sensitivity enhanced gradient NMR experiments for measuring interference effects between chemical shift anisotropy (CSA) and dipolar coupling interactions in a scalar coupled two-spin system in both the laboratory and rotating frames. We apply these methods for quantitative measurement of longitudinal and transverse cross-correlation rates involving interference of 13C CSA and 13C-1H dipolar coupling in a disaccharide, α,α-D-trehalose, at natural abundance of 13C as well as interference of amide 15N CSA and 15N-1H dipolar coupling in uniformly 15N-labeled ubiquitin. We demonstrate that the standard heteronuclear T1, T2, and steady-state NOE autocorrelation experiments augmented by cross-correlation measurements provide sufficient experimental data to quantitatively separate the structural and dynamic contributions to these relaxation rates when the simplifying assumptions of isotropic overall tumbling and an axially symmetric chemical shift tensor are valid.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Condensed Matter Physics