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A Case Study of the Conformation of Poly(alpha-aminoisobutyric acid): alpha- or 310-Helix

Prasad, BV Venkataram and Sasisekharan, V (1979) A Case Study of the Conformation of Poly(alpha-aminoisobutyric acid): alpha- or 310-Helix. In: Macromolecule, 12 (6). pp. 1107-1110.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ma60072a019

Abstract

The relative stabilities of a- and Blo-helical structures for polymers of a-aminoisobutyric acid (Aib) have been worked out, using the classical potential energy functions. To make a comparative study, we have used Buckingham "6-exp" and Kitaigorodsky's potential functions. Conformational analysis of the dipeptide segment with Aib residue indicates the necessity for nonplanar distortion of the peptide unit, which is a common feature in the observed crystal structures with Aib residues. In the range of Aw -10 to +loo studied, a-helical conformations are preferred in the region -3" < Aw < +loo, and Blo-helical conformations are preferred in the region -3" > Aw > -10'. Minimum energy conformations for right-handed structures are found in the +ue region of Aw and correspondingly for left-handed structures in the -ue region of Aw. For Aw - 6", a-helical structures have four- or near fourfold symmetry with h - 1.5 A. Such a helix with n = 4 and h = 1.5 A is termed an a'-helix. This structure is found to be consistent with the electron diffraction data of Malcolm3 and energetically more favorable than the standard 310-helix.

Item Type: Journal Article
Additional Information: Copy right of this article belongs to American Chemical Society.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 26 Oct 2009 06:34
Last Modified: 19 Sep 2010 05:49
URI: http://eprints.iisc.ernet.in/id/eprint/24293

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