Effects of end group and aggregation on helix conformation: Crystal structure of Ac-(Aib-Val-Ala-Leu)2-Aib-OMe

Karle, I. L. ; Flippen-Anderson, J. L. ; Uma, K. ; Balaram, P. (1996) Effects of end group and aggregation on helix conformation: Crystal structure of Ac-(Aib-Val-Ala-Leu)2-Aib-OMe Journal of Peptide Science, 2 (2). pp. 106-116. ISSN 1075-2617

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Official URL: http://www3.interscience.wiley.com/journal/24511/a...

Related URL: http://dx.doi.org/10.1002/psc.52

Abstract

The role of end groups in determining stereochemistry and packing in hydrophobic helical peptides has been investigated using an α-aminosobutyric acid (Aib) containing model nonapeptide sequence. In contrast to the Boc-analogue, Ac-(Aib-Val-Ala-Leu)2-Aib-OMe crystallizes with two independent molecules in a triclinic cell. The cell parameters are: space group P1, a=10.100(2)Å, b=15.194(4) Å, c=19.948(5) Å, α=63.12(2)°, β=88.03(2)°, γ=88.61(2)°, Z=2, R=7.96% for 5140 data where |Fo|>3σ(F). The two independent molecules alternate in infinite columns formed by head-to-tail hydrogen bonding. The helices in the two independent molecules are quite similar to each other but one molecule is rotated ≈123° about its helix axis with respect to the other. All the helical columns pack parallel to each other in the crystal. Replacement of the bulky Boc group does not lead to any major changes in conformation. Packing characteristics are also similar to those observed for similar helical peptides.

Item Type:Article
Source:Copyright of this article belongs to European Peptide Society.
Keywords:All Parallel Helix Assemblies; Helix Transition; 310/A-HELICES; Two Conformers; Water Associated With Non-polar Helices; X-ray Crystallography
ID Code:4886
Deposited On:18 Oct 2010 06:19
Last Modified:16 May 2016 15:28

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