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Observation of a mixed antiparallel and parallel beta-sheet motif in the crystal structure of Boc-Ala-Ile-Aib-OMe

Datta, S and Shamala, N and Gurunath, R and Balaram, P (1996) Observation of a mixed antiparallel and parallel beta-sheet motif in the crystal structure of Boc-Ala-Ile-Aib-OMe. In: International Journal of Peptide & Protein Research, 48 (3). pp. 209-214.

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Official URL: http://www.ncbi.nlm.nih.gov/pubmed/8897087

Abstract

A diastereomeric mixture of the tripeptide Boc-Ala-Ile-Aib-OMe crystallized in the space group P1 from CH3OH/H2O. The unit cell parameters are a = 10.593(2) A, b = 14.377(3) A, c = 17.872(4) A, alpha = 104.41(2) degrees, beta = 90.55(2) degrees, gamma = 106.91(2) degrees, V = 2512.4 A3, Z = 4. X-Ray crystallographic studies show the presence of four molecules in the asymmetric unit consisting of two pairs of diastereomeric peptides, Boc-L-Ala-L-Ile-Aib-OMe and Boc-L-Ala-D-Ile-Aib-OMe. The four molecules in the asymmetric unit form a rarely found mixed antiparallel and parallel beta-sheet hydrogen bond motif. The Ala and (L,D)-Ile residues in all the four molecules adopt the extended conformations, while the phi, psi values of the Aib residues are in the right-handed helical region. In one of the molecules the Ile sidechain adopts the unusual gauche conformation about the C beta-C gamma bond.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Munksgaard int pub ltd.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 22 Jan 2010 06:39
Last Modified: 22 Jan 2010 06:39
URI: http://eprints.iisc.ernet.in/id/eprint/24726

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