# Stereochemistry of \alpha-Aminoisobutyric Acid Peptides in Solution: Conformations of Decapeptides with a Central Triplet of Contiguous L-Amino Acids

Balaram, Hemalatha and Sukumar, M and Balaram, P (1986) Stereochemistry of \alpha-Aminoisobutyric Acid Peptides in Solution: Conformations of Decapeptides with a Central Triplet of Contiguous L-Amino Acids. In: Biopolymers, 25 (11). pp. 2209-2223.

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## Abstract

The decapeptides $Boc-Aib-L-Val-Aib-Aib-{(L-Val)}_3-Aib-L-Val-Aib-OMe$ and $Boc-Aib-L-Leu- Aib-Aib-{(L-Leu)}_3-Aib-L-Leu-Aib-OMe$ have been studied in $CD{Cl}_3$ and ${({CD}_3)}_2SO$ solutions by 270-MHz' H-nmr. In $CD{Cl}_3$ the presence of eight intramolecularly hydrogen-bonded NH groups has been established, consistent with a $3_{10}$-helical conformation, for both decapeptides. In ${({CD}_3)}_2SO$ only seven solvent-shielded NH groups are observed, supporting either an \alpha-helical conformation or a partially unfolded $3_{10}$-helix. Ir studies provided supporting evidence for intramolecularly hydrogen-bonded structures in $CH{Cl}_3$, while CD studies suggest helical conformation in both decapeptides in various solvents. CD studies also support helical folding in the C-terminal hexapeptides. The central triplet of L-amino acids appears to destabilize $3_{10}$-helical conformations in polar solvents like ${({CD}_3)}_2SO$.

Item Type: Journal Article http://www3.interscience.wiley.com/cgi-b... Copyright for this article belongs to John Wiley & Sons, Inc. Division of Biological Sciences > Molecular Biophysics Unit 01 Mar 2005 19 Sep 2010 04:18 http://eprints.iisc.ernet.in/id/eprint/2856