A deuterium NMR study of gramicidin A’

This thesis presents the results of the first application of a novel solid state nuclear magnetic resonance technique (K. P. Pauls et. al., Eur. Biophys. J. 11:1) to a naturally occuring membrane polypeptide. Deuterium NMR was used to study the structure and dynamics of hydrogen-exchanged gramicidin A', an ion channel, in model membranes. The technique exploits recently developed procedures for solvent-signal suppression (P. T. Callaghan et. al., J. Magn. Reson. 56:101), and "depakeing" powder spectra (E. Sternin, M.Sc. Thesis,U.B.C.). The spectra of gramicidin A' in crystalline form, and in the gel phase of the lipid bilayer are similar and indicate little molecular motion on the NMR timescale. In the liquid crystalline phase, however, the spectra suggest rapid uniaxial rotation of the gramicidin about the bilayer director. The frequencies of the liquid crystalline phase spectra were found to be independent of bilayer thickness, temperature, and the presence of sodium chloride, in the ranges investigated. The results are discussed in the context of the conduction properties of the gramicidin ion channel, other spectroscopic studies, and thecretical models of the structure and action of gramicidin.Science, Faculty ofPhysics and Astronomy, Department ofGraduat