Type II beta-turn conformation of pivaloyl-L-prolyl-a-aminoiso-butyryl-N-methylamide: Theoretical, spectroscopic and X-ray studies

Prasad, BV Venkataram and Balaram, Hemalatha and Balaram, P (1982) Type II beta-turn conformation of pivaloyl-L-prolyl-a-aminoiso-butyryl-N-methylamide: Theoretical, spectroscopic and X-ray studies. In: Biopolymers, 21 (7). pp. 1261-1273.

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Abstract

Pivaloyl-L-Pro-Aib-N-methylamihdaes been shown to possess one intramolecular hydrogen bond in (CD&SO solution, by 'H-nmr methods, suggesting the existence of p-turns, with Pro-Aib as the corner residues. Theoretical conformational analysis suggests that Type II P-turn conformations are about 2 kcal mol-' more stable than Type 111 structures. A crystallographic study has established the Type I1 /%turn in the solid state. The molecule crystallizes in the space group P21 with a = 5.865 8, b = 11.421 A, c = 12.966 A, /3 = 97.55", and 2 = 2. The structure has been refined to a final R value of 0.061. The Type I1 p-turn conformation is stabilized by an intramolecular 4 - 1 hydrogen bond between the methylamide NH and the pivaloyl CO group. The conformational angles are @pro= -57.8", $pro = 139.3', @Aib = 61.4', and $Ajb = 25.1'. The Type 11 /%turn conformation for Pro-Aib in this peptide is compared with the Type I11 structures observed for the same segment in larger peptides.

Item Type:	Journal Article
Publication:	Biopolymers
Publisher:	John Wiley & Sons
Additional Information:	Copyright of this article belongs to John Wiley & Sons.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	19 Feb 2010 09:47
Last Modified:	19 Sep 2010 05:55
URI:	http://eprints.iisc.ac.in/id/eprint/25685

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