ISSN:
0749-1581
Keywords:
1H NMR
;
13C NMR
;
β-Turn
;
Cyclic hexapeptide
;
Cis-trans
;
Isomerism
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The solution conformation of cyclo-(Pro-Pro-Gly)2 in CDCl3 and DMSO-d6 was investigated by 1H and 13C NMR spectroscopy. In CDCl3 solution the peptide maintains a conformational homogeneity at 300 K and the single asymmetric conformation observed is characterized by a single Pro-Pro cis-peptide bond and an intramolecularly hydrogen-bonded β-bend structure involving C=O of one glycine to the NH of the other glycine. The segment Gly-Pro-Pro-Gly responsible for the β-bend has a Pro-Pro peptide bond in the trans configuration. However, in DMSO-d6 solution, there is a conformational heterogeneity and the population of the two main conformers present is in the ratio of ca. 80:20. The major component is characterized as having two contiguous cis-peptide bonds involving Gly-Pro and Pro-Pro peptide bonds, while the minor component has a conformation characterized by a single Pro-Pro cis-peptide bond which is included in the β-bend structure. The equilibrium between the major and minor components is insensitive to temperature in the range 300--360 K. However, the conformational homogeneity in CDCl3 solution appears to be disturbed by addition of DMSO-d6 and becomes detectable beyond 20% (v/v) of DMSO-d6 and at 50:50 (v/v) the populations of the major and minor components become almost equal.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260311013
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