Motional properties are important for understanding protein function and are accessible to NMR relaxation measurements. The goal of this study is to investigate the internal dynamics occurring in gramicidin A (gA) channels in order to provide benchmark experimental data for comparison with the results of molecular dynamics simulations. We therefore synthesized several
15N isotope-enriched gA samples, covering all backbone residues as well as the Trp indole side chains for NMR relaxation experiments. On the basis of the
15N NMR spectra for labeled gA samples incorporated in sodium dodecylsulfate (SDS) micelles, we determined
T1,
T2, and heteronuclear NOE values for backbone and indole
15NH groups. The results indicate that the SDS-incorporated gA channel is a constrained structure without an especially 鈥渇loppy鈥?region. The NMR observables, particularly those for backbone groups, are predicted well by the molecular dynamics simulations in the accompanying article (DOI
10.1021/jp200904d).