Helix and hairpin nucleation in short peptides using centrally positioned conformationally constrained dipeptide segments

Chandrappa, Siddappa and Aravinda, Subrayashastry and Raghothama, Srinivasarao and Sonti, Rajesh and Rai, Rajkishor and Harini, Veldore V and Shamala, Narayanaswamy and Balaram, Padmanabhan (2012) Helix and hairpin nucleation in short peptides using centrally positioned conformationally constrained dipeptide segments. In: Organic and Biomolecular Chemistry, 10 (14). pp. 2815-2823.

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Abstract

The effect of incorporation of a centrally positioned Ac(6)c-Xxx segment where Xxx = (L)Val/(D)Val into a host oligopeptide composed of L-amino acid residues has been investigated. Studies of four designed octapeptides Boc-Leu-Phe-Val-Ac(6)c-Xxx-Leu-Phe-Val-OMe (Xxx = (D)Val 1, (L)Val 2) Boc-Leu-Val-Val-Ac(6)c-Xxx-Leu-Val-Val-OMe (Xxx = (D)Val 3, (L)Val 4) are reported. Diagnostic nuclear Overhouse effects characteristic of hairpin conformations are observed for Xxx = (D)Val peptides (1 and 3) while continuous helical conformation characterized by sequential NiH <-> Ni+1H NOEs are favored for Xxx = (L)Val peptides (2 and 4) in methanol solutions. Temperature co-efficient of NH chemical shifts are in agreement with distinctly different conformational preferences upon changing the configuration of the residue at position 5. Crystal structures of peptides 2 and 4 (Xxx = (L)Val) establish helical conformations in the solid state, in agreement with the structures deduced from NMR data. The results support the design principle that centrally positioned type I beta-turns may be used to nucleate helices in short peptides, while type I' beta-turns can facilitate folding into beta-hairpins.

Item Type:	Journal Article
Publication:	Organic and Biomolecular Chemistry
Publisher:	Royal Society of Chemistry
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:	20 Apr 2012 12:40
Last Modified:	20 Apr 2012 12:40
URI:	http://eprints.iisc.ac.in/id/eprint/44364

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