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Conformational Interconversions in Peptide beta-Turns: Discrimination Between Enantiomeric Conformations by Chiral Perturbation

Raghothama, S and Chaddha, Manjula and Banumathi, S and Ravikumar, Krishnan and Velmurugan, D and Balaram, P (1998) Conformational Interconversions in Peptide beta-Turns: Discrimination Between Enantiomeric Conformations by Chiral Perturbation. In: Biopolymers, 45 (3). pp. 191-202.

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Abstract

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’ beta-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 beta-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’ beta-turns. The isomeric peptide, Boc-Gly-Leu-Aib-Ome (2) , adopts an ‘‘open’’ type II’ b-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.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to John Wiley & Sons, Inc.
Keywords: Conformational interconversions;Peptide beta-turns;Enantiomeric conformations;Chiral perturbations
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Chemical Sciences > Sophisticated Instruments Facility
Date Deposited: 12 Oct 2004
Last Modified: 19 Sep 2010 04:16
URI: http://eprints.iisc.ernet.in/id/eprint/2093

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