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C12-Helix development in ()n sequences - spectroscopic characterization of Boc-Aib-4(R)Val]-OMe oligomers

Dinesh, Bhimareddy and Vinaya, Vishwanathan and Raghothama, Srinivasarao and Balaram, Padmanabhan (2013) C12-Helix development in ()n sequences - spectroscopic characterization of Boc-Aib-4(R)Val]-OMe oligomers. In: European Journal of Organic Chemistry (17). pp. 3590-3596.

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Official URL: http://dx.doi.org/10.1002/ejoc.201300264

Abstract

The solution conformations of the -hybrid oligopeptides Boc-Aib-4(R)Val]n-OMe (n = 1-8) in organic solvents have been probed by NMR, IR, and CD spectroscopic methods. In the solid state, this peptide series favors C12-helical conformations, which are backbone-expanded analogues of 310 helices in -peptide sequences. NMR studies of the six- (n = 3) and 16-residue (n = 8) peptides reveal that only two NH protons attached the N-terminus residues Aib(1) and 4(R)Val(2) are solvent-exposed. Sequential NiH-Ni+1H NOEs characteristic of local helical conformations are also observed at the residues. IR studies establish that chain extension leads to a large enhancement in the intensities of the hydrogen-bonded NH stretching bands (3343-3280 cm-1), which suggest elongation of intramolecularly hydrogen-bonded structures. The development of C12-helical structures upon lengthening of the sequence is supported by the NMR and IR observations. The CD spectra of the ()n peptides reveal a negative maximum at ca. 206 nm and a positive maximum at ca. 192 nm, spectral feature that are distinct from those of 310 helices in -peptides.

Item Type: Journal Article
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Additional Information: Copyright of this article belongs to John Wiley and Sons.
Keywords: Peptides; Amino Acids; Helical Structures; Conformation Analysis
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Chemical Sciences > NMR Research Centre (Formerly SIF)
Date Deposited: 19 Jul 2013 07:17
Last Modified: 19 Jul 2013 07:17
URI: http://eprints.iisc.ernet.in/id/eprint/46854

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