Solution‐phase chemical shift anisotropy as a promising tool to probe intermolecular interactions and peptide bond geometry: a case study on 15 N‐labeled N α ‐ t ‐Boc‐ L ‐valine

Geometry‐dependent chemical shift anisotropy (CSA g ) values of 1 H and 15 N nuclei have been determined in solution for 15 N‐labeled, N α ‐ t ‐Boc‐ L ‐valine by measurements of CSA/dipole–dipole cross‐correlated relaxation rates using longitudinal variants of the recently proposed one‐dimensional cross‐correlation experiments. We demonstrate that solvent dependence of the CSA g is an invaluable tool for monitoring intermolecular H‐bonding interactions. In addition, enhanced temperature dependence was observed for CSA g , which indicates that the anisotropy of chemical shift is more sensitive to subtle changes in the electronic environment of the nucleus than the motionally averaged isotropic chemical shift. 15 N CSA g values have been determined in cyclosporin A at natural isotope abundance using the proposed 1 H‐detected pulse schemes. A remarkable correlation was observed between the measured 15 N CSA g and the peptide ω angle, taken from the X‐ray structure of cyclosporin A. Copyright © 2003 John Wiley & Sons, Ltd.