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Signature of n→π* interactions in α-helices

✍ Scribed by Amit Choudhary; Ronald T. Raines

Publisher
Cold Spring Harbor Laboratory Press
Year
2011
Tongue
English
Weight
429 KB
Volume
20
Category
Article
ISSN
0961-8368

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✦ Synopsis

Abstract

The oxygen of a peptide bond has two lone pairs of electrons. One of these lone pairs is poised to interact with the electron‐deficient carbon of the subsequent peptide bond in the chain. Any partial covalency that results from this n→π* interaction should induce pyramidalization of the carbon (C′~i~) toward the oxygen (O~i−1~). We searched for such pyramidalization in 14 peptides that contain both α‐ and β‐amino acid residues and that assume a helical structure. We found that the α‐amino acid residues, which adopt the main chain dihedral angles of an α‐helix, display dramatic pyramidalization but the β‐amino acid residues do not. Thus, we conclude that O~i−1~ and C′~i~ are linked by a partial covalent bond in α‐helices. This finding has important ramifications for the folding and conformational stability of α‐helices in isolation and in proteins.

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