Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2005. / Vita. Includes bibliographical references.

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 of / Physics and Astronomy, Department of / Graduate

The studies presented in this thesis are in two areas. An investigation of aromatic nitrene molecules using EPR spectroscopy was undertaken. This revealed a general tendency for these molecules to exhibit two forms when trapped in a crystalline lattice. This is qualitatively interpreted as a perturbing effect of nitrogen evolved during generation from the azide. Single crystal experiments were made on 2,4,6-tribromophenyl nitrene, which exhibited an unusually large anisotropy in the zero field splitting, implying a bent structure. Temperature variation of several aromatic nitrene zero field splittings were made. The variation was interpreted as thermal averaging amongst states possessing different zero field parameters. The nature of these states however, could not be inferred. The variation is compared with similar studies. A computer program to least squares fit EPR angular data to a spin Hamiltonian has been written. This programme was used to obtain a description of the angularly dependent EPR data from an aromatic nitrene, and also for a radical species with a large hyperfine interaction. / Science, Faculty of / Chemistry, Department of / Graduate

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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy