Nagaraj, R and Venkatachalapathi, YV and Balaram, P (1980) Rotational isomerism about the Ca-CO bond in proline derivatives. 1H and 13C NMR studies of benzyloxycarbonyl-Pro-N-methylamide and pivaloyl-Pro-N-methylamide. In: Journal of Peptide Research, 16 (4). 291 -298.
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The 270 MHz 1H n.m.r. spectrum of benzyloxycarbonyl-Pro-N-methylamide in CDCl3 is exchange broadened at 293° K. Spectral lines due to two species are frozen out at 253° K and a dynamically averaged spectrum is obtained at 323° K. A selective broadening of the Cβ and Cγ resonances in the 13C n.m.r. spectrum is observed at 253° K, with a splitting of the Cβ and Cγ resonances into a pair of lines of unequal intensity. A similar broadening of Cβ and Cγ peaks is also detected in pivaloyl-Pro-N-methylamide where cis-trans interconversion about the imide bond is precluded by the bulky t-butyl group. The rate process is thus attributed to rotation about the Cα-CO bond (ψ) and a barrier (ΔG#) of 14kcal mol-1 is estimated. 13C n.m.r. data for pivaloyl-Pro-N-methylamide in a number of solvents is presented and the differences in the Cβ and Cγ chemical shifts are interpreted in terms of rotational isomerism about the Cα-CO bond.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to John Wiley and Sons.|
|Keywords:||activation barriers;nuclear magnetic resonance;peptide conformation;proline;rotational isomerism.|
|Department/Centre:||Division of Biological Sciences > Molecular Biophysics Unit|
|Date Deposited:||22 Feb 2010 09:09|
|Last Modified:||19 Sep 2010 05:55|
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