Nuclear Magnetic Resonance Linewidth Studies of Model Membranes

• Main Author: Seiter, Charles Harrington
• Format: Others
• Language: en
• Published: 1974
• Online Access: https://thesis.library.caltech.edu/14119/2/Seiter_CH_1974.pdf; Seiter, Charles Harrington (1974) Nuclear Magnetic Resonance Linewidth Studies of Model Membranes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/bmyt-e427. https://resolver.caltech.edu/CaltechTHESIS:04082021-230959216 <https://resolver.caltech.edu/CaltechTHESIS:04082021-230959216>

<p>The possible applications of magnetic resonance spectroscopy to current problems in membrane biophysics are surveyed with a particular view to the use of newer Fourier transform and multipulse techniques. Two contributions to this field are presented. The first contribution describes a Fourier transform filtering technique which removes the broad proton magnetic resonance (pmr) lines characteristic of cell membranes and unsonicated lipid bilayers to allow observation of methyl proton and other sharp resonance peaks. The interaction of valinomycin with lipid bilayers is monitored by this method, and the valinomycin is found to interact primarily with the polar choline head groups of the lecithin molecules in the bilayer. The second contribution analyzes the pmr linewidths of sonicated and unsonicated bilayers by the stochastic linewidth method of P. W. Anderson. It is found that the local packing of lipid chains in sonicated vesicles is significantly less orderly than the local packing in unsonicated bilayers. It is also shown that the sharp methyl resonances observed in pmr spectra of unsonicated bilayers correspond to the central spike characteristic of the methyl rotor dipolar powder spectrum in solids, and that this powder spectrum is only partially averaged by the restricted molecular motions available to lipids in unsonicated bilayers. Finally, a Waugh multipulse spectrum of unsonicated bilayers is used to establish kink formation on a timescale of 10^-7 sec as the chief mode of local molecular motion for protons on lipid hydrocarbon chains in unsonicated systems, as compared to trans-gauche bond rotations on a timescale of 5 x 10^-9 sec or faster as the mode of local motion of protons in sonicated vesicles. The value of these two systems as model membranes is discussed in the light of these motional results.</p>