Conformational properties and aggregation of homo-oligomeric beta(3)(R)-valine peptides in organic solvents

Vasantha, Basavalingappa and Yamanappa, Hunashal and Raghothama, Srinivasarao and Balaram, Padmanabhan (2017) Conformational properties and aggregation of homo-oligomeric beta(3)(R)-valine peptides in organic solvents. In: BIOPOLYMERS, 108 (3).

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Abstract

The conformational characteristics of protected homo-oligomeric Boc-beta(3)(R) Val](n)-OMe, n = 1, 2, 3, 4, 6, 9, and 12 have been investigated in organic solvents using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) absorption spectroscopy and circular dichroism (CD) methods. The detailed H-1 NMR analysis of Boc-beta(3)(R)Val](12)-OMe reveals that the peptide aggregates extensively in CDCl3, but is disaggregated in 20%, (v/v) dimethyl sulfoxide (DMSO) in CDCl3 and in CD3OH. Limited assignment of the N-terminus NH groups, together with solvent dependence of NH chemical shifts and temperature coefficients provides evidence for 14-helix conformation in the 12-residue peptide. FTIR analysis in CHCl3 establishes that the onset of folding and aggregation, as evidenced by NH stretching bands at 3375 cm(-1) (intramolecular) and 3285 cm(-1) (intermolecular), begins at the level of the tetrapeptide. The observed CD bands, 214 nm (negative) and 198 nm (positive), support 14-helix formation in the 9 and 12 residue sequences. The folding and aggregation tendencies of homo-oligomeric alpha-, beta-, and gamma-residues is compared in the model peptides Boc-omega Val] omega-NHMe, omega = alpha, beta, and gamma and n = 1, 2, and 3. Analysis of the FTIR spectra in CHCl3, establish that the tendency to aggregate at the di and tripeptide level follows the order beta > alpha similar to gamma, while the tendency to fold follows the order gamma > beta > alpha.

Item Type:	Journal Article
Publication:	BIOPOLYMERS
Additional Information:	Copy right for this article belongs to the WILEY, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	09 Sep 2017 04:36
Last Modified:	09 Sep 2017 04:36
URI:	http://eprints.iisc.ac.in/id/eprint/57770

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