The structural motif and backbone dynamics of the gramicidin-A transmembrane channel in a membrane environment have been investigated using solid-state $\sp{15}$N NMR. Recent determinations of the $\sp{15}$N chemical shift anisotropy tensor with respect to the molecular frame enable the quantitative evaluation of the $\sp{15}$N chemical shift resonances obtained from oriented dimyristoylphosphatidylcholine (DMPC) bilayer samples containing specific-site $\sp{15}$N-labeled gramicidin. / Spectra obtained from oriented samples in the liquid-crystalline phase have been used to verify the $\beta$-type hydrogen-bonding pattern of the helical backbone, and to determine that in these DMPC bilayer preparations the gramicidin channel is right-handed. In addition, these data place constraints on the C$\sb\alpha$-C$\sb\alpha$ axis orientation of individual peptide planes relative to the helix axis. / Spectra obtained from oriented samples in the gel phase have been analyzed to yield a spatial model for local motion. This model includes the axis of motion, the mean orientation, and the maximum amplitude of displacement for individual peptide planes. Specific sites in the first turn of the amino terminus were investigated, with emphasis on the Ala$\sb3$ and Leu$\sb4$ linkages for which the orientation of the $\sp{15}$N tensor with respect to the molecular frame has been determined. The effects of two well defined smectic layer defect structures, parabolic focal conics (PFC's) and oily streaks, are included in the spectral simulations. It is concluded that in the absence of ions, large amplitude motions are not present in the peptide planes of the first turn of the helix. A detailed characterization of bilayer surface geometry is presently the limiting factor in the use of this technique for probing the spatial extent of local motions in integral membrane proteins. / Source: Dissertation Abstracts International, Volume: 51-04, Section: B, page: 1604. / Major Professor: Timothy Albert Cross. / Thesis (Ph.D.)--The Florida State University, 1990.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78250 |
| Contributors | Nicholson, Linda Kay., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 160 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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