Negative nuclear Overhauser effects as probes of macromolecular structure

Balaram, P and Bothner, AA and Dadok, J (1972) Negative nuclear Overhauser effects as probes of macromolecular structure. In: Journal of the American Chemical Society., 94 (11). pp. 4015-4017.

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Abstract

Nuclear Overhauser effects (NOE) and circular dichroism (CD) techniques have been used to probe @-turn conformations in acyclic and cyclic peptides containingPro-Xsequences. The model peptides studied are of the type Piv-Pro-X-NHMe (X = Aib, D-Ala, Gly, Val, and Leu) and Boc-Cys-Pro-X-C s NHMe (X = Aib, L-Ala, D-Ala, Gly, and Leu). In the acyclic series, observation of NOES between Pro C"H and X-NH, together with solvent and temperature dependence of NH chemical shifts, establishes a 4 - 1 hydrogen bond stabilized type I1 @-turn in the Gly, D-Ala, and Aib peptides, in CDC13 and (CD3)2S0. A positive n-r* CD band at -225-230 nm appears to be characteristic of this structure. For the acyclic Pro-Leu peptide the observation of NOE's for both Pro and Leu C"H resonances on saturation of Leu NH is compatible with a type V bend or consecutive y-turn conformation. In the cyclic disulfide series the Pro-Aib and Pro-D-Ala peptides favor type I1 @-turns, whereas all other peptides adopt type I (111) conformations. All the cyclic disulfides exhibit an intense negative CD band at -228-230 nm. The results suggest thatgeneralcorrelations between CD spectral type and specific 0-turn conformations may not be obtained. Evidence for solvent-dependent structural changes in the Pro-Aib sequence in both cyclic and acyclic peptides is presented.

Item Type:	Journal Article
Publication:	Journal of the American Chemical Society.
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	20 May 2010 04:38
Last Modified:	19 Sep 2010 06:00
URI:	http://eprints.iisc.ac.in/id/eprint/27162

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