The Application of 'Magic Angle' Sample Spinning NMR to the Study of Liquid Crystals and Membranes
Forbes, Jeffrey Garner
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https://hdl.handle.net/2142/70422
Description
Title
The Application of 'Magic Angle' Sample Spinning NMR to the Study of Liquid Crystals and Membranes
Author(s)
Forbes, Jeffrey Garner
Issue Date
1988
Doctoral Committee Chair(s)
Oldfield, Eric
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Abstract
Proton and Carbon-13 "Magic Angle" Sample Spinning (MASS) NMR is shown to yield high-resolution spectra for a variety of fluid liquid crystalline phases. Relatively slow ca. 3-kHz MASS causes averaging of the broadening interactions in both $\sp $C and $\sp1$H spectra of liquid crystals. Due to the special form of the $\sp1$H-$\sp1$H dipole Hamiltonian in liquid crystals, the interactions are inhomogeneous and slow MASS gives rise to a highly resolved spectrum with spinning sidebands. The chemical shift anisotropy of the carbons in fluid liquid crystals is small enough that slow mass completely averages the interaction. The resolution of both $\sp $C and $\sp1$H MASS NMR spectra of multilamellar dispersions is as good as with sonicated dispersions. MASS allows much more concentrated samples to be studied and accordingly the spectra may be recorded much faster. When sterols are added to lipid membranes, $\sp $C MASS NMR gives highly resolved one and two carbon resonances for all the sterol carbons, whereas with sonicated dispersions most resonances are very broad and several cannot be observed at all. A variety of lipid and lipid-sterol dispersions are studied, as well as the natural membrane myelin, where over 50 peaks can be observed and ca. 40 of these may be assigned to specific, single-carbon atom sites in the membrane. The high resolution obtained with MASS NMR allows relaxation times to be measured for single carbon atoms in the lipid and sterol molecules. The slow motions in some model and natural membrane systems are studied with rotating frame spin-lattice relaxation times, $T\sb{1\rho}$, measured directly and through the CP/MASS experiment.
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