Tryptophan-containing peptide helices: interactions involving the indole side chain

Mahalakshmi, R and Sengupta, A and Raghothama, S and Shamala, N and Balaram, P (2005) Tryptophan-containing peptide helices: interactions involving the indole side chain. In: Journal of Peptide Research, 66 (5). pp. 277-296.

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Abstract

TTwo designed peptide sequences containing Trp residues at positions i and i + 5 ( Boc- Leu- Trp- Val- Ala- Aib- Leu- Trp- Val- OMe, 1) as well as i and i + 6 ( Boc- Leu- Trp- Val- Aib- Ala- Aib- Leu- Trp-Val-OMe, 2) containing one and two centrally positioned Aib residues,respectively, for helix nucleation, have been shown to form stable helices in chloroform solutions. Structures derived from nuclear magnetic resonance ( NMR) data reveal six and seven intramolecular lyhydrogen- bonded NH groups in peptides 1 and 2, respectively. The helical conformation of octapeptide 1 has also been established in the solid state by X- ray diffraction. The crystal structure reveals an interesting packing motif in which helical columns are stabilized by side chain - backbone hydrogen bonding involving the indole N epsilon 1H of Trp( 2) as donor, and an acceptor C=O group from Leu( 6) of a neighboring molecule. Helical columns also associate laterally, and strong interactions are observed between the Trp( 2) and Trp( 7)residues on neighboring molecules. The edge- to- face aromatic interactions between the indoles suggest a potential C- H. pi interaction involving the C zeta 3H of Trp( 2). Concentration dependence of NMR chemical shifts provides evidence for peptide association in solution involving the Trp( 2) N epsilon 1H protons,presumably in a manner similar to that observed in the crystal.

Item Type:	Journal Article
Publication:	Journal of Peptide Research
Publisher:	Blackwell Publishing
Additional Information:	Copyright for this article belongs to Blackwell Publishing.
Keywords:	aromatic interactions;C-H ���¦pi interactions;indole NH hydrogen bonding;nuclear magnetic resonance structures;peptide aggregation;tryptophan peptides
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit Division of Physical & Mathematical Sciences > Physics
Date Deposited:	29 Nov 2005
Last Modified:	19 Sep 2010 04:21
URI:	http://eprints.iisc.ac.in/id/eprint/4221

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