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Hybrid Peptide Hairpins Containing $\alpha$-and $\varpi$-Amino Acids: Conformational Analysis of Decapeptides with Unsubstituted $\beta$-, $\gamma$-, and $\delta$-Residues at Positions 3 and 8

Roy, Rituparna S and Gopi, Hosahudya N and Raghothama, Srinivasa Rao and Karle, Isabella L and Balaram, Padmanabhan (2006) Hybrid Peptide Hairpins Containing $\alpha$-and $\varpi$-Amino Acids: Conformational Analysis of Decapeptides with Unsubstituted $\beta$-, $\gamma$-, and $\delta$-Residues at Positions 3 and 8. In: Chemistry - A European Journal, 12 (12). 3295 -3302.

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Abstract

The effects of inserting unsubstituted -amino acids into the strand segments of model -hairpin peptides was investigated by using four synthetic decapeptides, Boc-Leu-Val-Xxx-Val-D-Pro-Gly-Leu-Xxx-Val-Val-OMe: peptide 1 (Xxx=Gly), peptide 2 (Xxx=$\beta$Gly=$\beta$ahGly=homoglycine, -$\beta$glycine), peptide 3 (Xxx=$\gamma$Abu=-$\gamma$aminobutyric acid), peptide 4 (Xxx=$\delta$Ava=-$\delta$aminovaleric acid). $^1H\hspace{2mm}NMR$ studies (500 MHz, methanol) reveal several critical cross-strand NOEs, providing evidence for -$\beta$hairpin conformations in peptides 2-4. In peptide 3, the NMR results support the formation of the nucleating turn, however, evidence for cross-strand registry is not detected. Single-crystal X-ray diffraction studies of peptide 3 reveal a -$\beta$hairpin conformation for both molecules in the crystallographic asymmetric unit, stabilized by four cross-strand hydrogen bonds, with the $\gamma$Abu residues accommodated within the strands. The D-Pro-Gly segment in both molecules (A,B) adopts a type II -$\beta$turn conformation. The circular dichroism spectrum for peptide 3 is characterized by a negative CD band at 229 nm, whereas for peptides 2 and 4, the negative band is centered at 225 nm, suggesting a correlation between the orientation of the amide units in the strand segments and the observed CD pattern.

Item Type: Journal Article
Additional Information: The copyright belongs to WILEY-VCH Verlag GmbH & Co. KGaA.
Keywords: Amino acids;Conformation;Analysis;Crystal structure;Peptides;Protein folding
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 13 Feb 2007
Last Modified: 19 Sep 2010 04:26
URI: http://eprints.iisc.ernet.in/id/eprint/6726

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