Synthetic Peptide Helices in Crystals: Structure and Antiparallel and Skewed Packing Motifs for \alpha-Helices in Two Isomeric Decapeptides

Karle, Isabella L and Flippen-Anderson, Judith L and Uma, K and Balaram, P (1990) Synthetic Peptide Helices in Crystals: Structure and Antiparallel and Skewed Packing Motifs for \alpha-Helices in Two Isomeric Decapeptides. In: Biopolymers, 30 (7-8). pp. 719-731.

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Abstract

The isomeric decapeptides Boc-Aib-Ala-Leu-Ala-Aib-Aib-Leu-Ala-Leu-Aib-OMe (II) and Boc- Aib-Ala-Aib- Ala-Leu-Ala-Leu-Aib-Leu- Aib-OMe (III) , are predominantly \alpha-helical with little effect on the conformation with interchange of Aib/Ala residues or Aib/Leu residues. The packing motif of helices in crystal II is antiparallel, whereas the helices pack in a skewed fashion in crystal III, with a 40 deg angle between neighboring helix axes. Crystal III contains a water molecule in a hydrophobic hole that forms hydrogen bonds with two carbonyl oxygens that also participate in 5 \rightarrow 1 type hydrogen bonds. Values for helical torsional angles \phi and \psi assume a much wider range than anticipated. Crystal II: C49H88N10O13, space group P21, with a = 16.625(2) A, b = 9.811 ( 5 ) A, c = 18.412(3) A, \beta = 99.79( l) deg, Z = 2, R = 5.7% for 4338 data with [Fo] > 3\sigma(F). Crystal III: C49H88N10O13.1/2H2O, space group P21 with a = 11.072 ( 2 ) A, b = 34.663( 5) A, c = 16.446( 3 ) A, = 107.85( 1 ) deg, Z = 4, R = 8.3% for 6087 data with [Fo] > 3\sigma(F).

Item Type:	Journal Article
Publication:	Biopolymers
Publisher:	John Wiley & Sons, Inc
Additional Information:	Copyright for this article belongs to John Wiley & Sons, Inc.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	24 Dec 2004
Last Modified:	19 Sep 2010 04:17
URI:	http://eprints.iisc.ac.in/id/eprint/2514

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