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Stereochemistry of α‐aminoisobutyric acid peptides in solution: Helical conformations of protected decapeptides with repeating Aib‐ L ‐Ala and Aib‐ L ‐Val sequences
Author(s) -
kumar E. K. S. Vijaya,
Balaram P.
Publication year - 1983
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360220911
Subject(s) - chemistry , intramolecular force , solvent , stereochemistry , crystallography , amino acid , organic chemistry , biochemistry
The decapeptides Boc‐(Aib‐ L ‐Ala) 5 ‐OMe and Boc‐(Aib‐ L ‐Val) 5 ‐OMe have been studied by 270‐MHz 1 H‐nmr in CDCl 3 and (CD 3 ) 2 SO 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 3 10 ‐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.