ISSN:
0006-3525
Keywords:
conformational interconversions
;
peptide β-turns
;
enantiomeric conformations
;
chiral perturbations
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The crystal structure of the model tripeptide Boc-Aib-Gly-Leu-OMe (1) reveals two independent molecules in the asymmetric unit that adopt “enantiomeric” type I and type I′ β-turn conformations with the Aib and Gly residues occupying the corner (i + 1 and i + 2) positions. 13C cross polarization and magic angle sample spinning spectra in the solid state also support the coexistence of two conformational species. 13C-nmr in CDCl3 establishes the presence of a single species or rapid exchange between conformations. 400 MHz 1H-nmr provides evidence for conformational exchange involving a major and minor species, with β-turn conformations supported by the low solvent exposure of Leu(3) NH and the observation of NiH ↔ Ni+1H nuclear Overhauser effects. CD bands in the region 190-230 nm are positive, supporting a major population of type I′ β-turns. The isomeric peptide, Boc-Gly-Leu-Aib-OMe (2), adopts an “open” type II′ β-turn conformation in crystals. Solid state and solution nmr support population of a single conformational species. Chiral perturbation introduced outside the folded region of peptides may provide a means of modulating screw sense in achiral sequences. © 1998 John Wiley & Sons, Inc. Biopoly 45: 191-202, 1998
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
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