Monoselective, Rio(SE), biselective, Rio(i,j), and nonselective proton spin-lattice relaxation rates have been measured for dilute solutions of gramicidin S in dimethyl sulfoxide and used to evaluate cross-relaxation rates (sigma ij = Rio(i,j)-Rio(SE)) and Fi ratios (Fi = Ri(NS)/Rio(SE)). The cross-relaxation parameters, sigma, and Fi ratios measured for backbone gramicidin S protons predict that the same correlation time, tau c = 1.2 X 10(-9)s, modulates all the dipolar proton-proton interactions and that these interactions represent the main source for the proton spin-lattice relaxation process. The larger relaxation rates for amide versus alpha-protons of the backbone are attributed to dipolar relaxation between 14N and its directly bonded protons and is an approximate measure of the extent of this. The intrabackbone proton-proton distances, evaluated from sigma values, were consistent with the antiparallel beta-plated sheet/beta II'-turn conformation previously proposed for gramicidin S in solution.
|Titolo:||Proton relaxation mechanisms and the measurements of r phi, r psi and transannular interproton distances in gramicidin S.|
|Citazione:||Niccolai, N., L., P., Rossi, C., P., C., & W. A., G. (1984). Proton relaxation mechanisms and the measurements of r phi, r psi and transannular interproton distances in gramicidin S. BIOPHYSICAL CHEMISTRY, 20, 217-223.|
|Appare nelle tipologie:||1.1 Articolo in rivista|
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