NMR Experiments for the measurement of carbon relaxation properties in l3C, I5N-labeled gramicidin channels

by Gu, Hong; Diaz, Jennifer; Hinton, James F.; Koeppe II, R. Erdman

Motional properties are important for understanding functional aspects of proteins and are accessible from NMR relaxation measurements. The goal of this study is to investigate the internal dynamics occurring in gramicidin A (gA) channels. We have synthesized several isotope-enriched gA samples, including [15N-(Val1,Gly2,Ala3,Ala5,Val7)]gA, [15N-(Leu4 ,Val6 ,Val8 , Leu10, Leu12 , Leu14)] gA minus and [(15N,13C)-(Gly2,Ala5,Val7,Trp9)]gA, for the NMR relaxation expts. Based upon the 15N- and 13C-NMR spectra for labeled gA samples incorporated in SDS micelles, we have been able to det. T1 values for selected backbone carbonyl carbons, and T1, T2, and NOE values for selected backbone 15NH groups. In future work, these NMR observables will be compared with the predictions of mol. dynamics simulations.