A combined extended and helical backbone for Boc-(Ala-Leu-Ac7c-)2-OMe

Karle, I. L. ; Prasad, S. ; Balaram, P. (2004) A combined extended and helical backbone for Boc-(Ala-Leu-Ac7c-)2-OMe The Journal of Peptide Research, 63 (2). pp. 175-180. ISSN 1397-002X

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Official URL: http://www3.interscience.wiley.com/journal/1200934...

Related URL: http://dx.doi.org/10.1111/j.1399-3011.2003.00120.x


The structure of the peptide Boc-Ala-Leu-Ac7c-Ala-Leu-Ac7c-OMe (Ac7c,1-aminocycloheptane-1-carboxylic acid) is described in crystals. The presence of two Ac7c residues was expected to stabilize a 310-helical fold. Contrary to expectation the structural analysis revealed an unfolded amino terminus, with Ala(1) adopting an extended β-conformation (φ = -93°, ψ = 112°). Residues 2-5 form a 310-helix, stabilized by three successive intramolecular hydrogen bonds. Notably, two NH groups Ala(1) and Ac7c(3) do not form any hydrogen bonds in the crystal. Peptide assembly appears to be dominated by packing of the cycloheptane rings that stack against one another within the molecule and also throughout the crystal in columns.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
Keywords:Crystal Structure Analysis; Helix with Extended Backbone; Lack of Hydrogen-bond Formation; Stacking of Cycloheptyl Rings
ID Code:4912
Deposited On:18 Oct 2010 06:14
Last Modified:16 May 2016 15:29

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