Stereochemistry of α-aminoisobutyric acid peptides in solution: helical conformations of protected decapeptides with repeating Aib-L-Ala and Aib-L-Val sequences

Vijayakumar, E. K. S. ; Balaram, P. (1983) Stereochemistry of α-aminoisobutyric acid peptides in solution: helical conformations of protected decapeptides with repeating Aib-L-Ala and Aib-L-Val sequences Biopolymers, 22 (9). pp. 2133-2140. ISSN 0006-3525

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Official URL: http://www3.interscience.wiley.com/journal/1075878...

Related URL: http://dx.doi.org/10.1002/bip.360220911

Abstract

The decapeptides Boc-(Aib-L-Ala)5-OMe and Boc-(Aib-L-Val)5-OMe have been studied by 270-MHz 1H-nmr in CDCl3 and (CD3)2SO solutions. Intramolecular hydrogen-bonded NH groups have been delineated using the temperature and solvent dependence of the NH chemical shifts and differential broadening of the NH resonances, induced by addition of a nitroxide radical. Both peptides have eight solvent-shielded NH groups, suggesting that 310-helical conformations are maintained in the two solvents. In alternating Aib-X sequences, the Aib residues appear to play a dominant role in determining the preferred conformations, overriding the intrinsic stereochemical preferences of the X residues.

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