Karle, IL and Prasad, S and Balaram, P (2004) A combined extended and helical backbone for Boc-(Ala-Leu-Ac(7)c-)(2)-OMe. In: Journal of Peptide Research, The, 63 (2). pp. 175-180.
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The structure of the peptide Boc-Ala-Leu-Ac(7)c-Ala-Leu-Ac(7)c-OMe (Ac(7)c,1-aminocycloheptane-1-carboxylic acid) is described in crystals. The presence of two Ac(7)c residues was expected to stabilize a 3(10)-helical fold. Contrary to expectation the structural analysis revealed an unfolded amino terminus, with Ala(1) adopting an extended beta-conformation (phi = -93degrees,psi = 112degrees). Residues 2-5 form a 3(10)-helix, stabilized by three successive intramolecular hydrogen bonds. Notably, two NH groups Ala(1) and Ac(7)c(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:||Journal Article|
|Additional Information:||Copy right of this article belongs to John Wiley and Sons.|
|Keywords:||crystal structure analysis; helix with extended backbone; lack of hydrogen-bond formation; stacking of cycloheptyl rings.|
|Department/Centre:||Division of Biological Sciences > Molecular Biophysics Unit|
|Date Deposited:||29 Apr 2010 10:01|
|Last Modified:||19 Sep 2010 06:01|
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