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Analysis of designed beta-hairpin peptides: molecular conformation and packing in crystals

Aravinda, Subrayashastry and Raghavender, Upadhyayula S and Rai, Rajkishor and Harini, Veldore V and Shamala, Narayanaswamy and Balaram, Padmanabhan (2013) Analysis of designed beta-hairpin peptides: molecular conformation and packing in crystals. In: Organic & Biomolecular Chemistry, 11 (25). pp. 4220-4231.

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Official URL: http://dx.doi.org/10.1039/C3OB25777K

Abstract

The crystal structures of several designed peptide hairpins have been determined in order to establish features of molecular conformations and modes of aggregation in the crystals. Hairpin formation has been induced using a centrally positioned (D)Pro-Xxx segment (Xxx = (L)Pro, Aib, Ac(6)c, Ala; Aib = alpha-aminoisobutyric acid; Ac(6)c = 1-aminocyclohexane-1-carboxylic acid). Structures of the peptides Boc-Leu-Phe-Val-(D)Pro-(L)Pro-Leu-Phe-Val-OMe (1), Boc-Leu-Tyr-Val-(D)Pro-(L)Pro-Leu-Phe-Val-OMe (2, polymorphic forms labeled as 2a and 2b), Boc-Leu-Val-Val-(D)Pro-(L)Pro-Leu-Val-Val-OMe (3), Boc-Leu-Phe-Val-(D)Pro-Aib-Leu-Phe-Val-OMe (4, polymorphic forms labeled as 4a and 4b), Boc-Leu-Phe-Val-(D)Pro-Ac(6)c-Leu-Phe-Val-OMe (5) and Boc-Leu-Phe-Val-(D)Pro-Ala-Leu-Phe-Val-OMe (6) are described. All the octapeptides adopt type II' beta-turn nucleated hairpins, stabilized by three or four cross-strand intramolecular hydrogen bonds. The angle of twist between the two antiparallel strands lies in the range of -9.8 degrees to -26.7 degrees. A detailed analysis of packing motifs in peptide hairpin crystals is presented, revealing three broad modes of association: parallel packing, antiparallel packing and orthogonal packing. An attempt to correlate aggregation modes in solution with observed packing motifs in crystals has been made by indexing of crystal faces in the case of three of the peptide hairpins. The observed modes of hairpin aggregation may be of relevance in modeling multiple modes of association, which may provide insights into the structure of insoluble polypeptide aggregates.

Item Type: Journal Article
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Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 15 Jul 2013 09:57
Last Modified: 15 Jul 2013 09:57
URI: http://eprints.iisc.ernet.in/id/eprint/46887

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