Capping Motif for Peptide Helix Formation

It is known that a C-terminal lysine stabilizes helix formation in polyalanine peptides that have seven or more residues. Using a combination of cold ion spectroscopy and DFT calculations, we demonstrate that even a three-residue peptide, Ac-Phe-Ala-LysH+, adopts a structure in which the lysine side chain forms three hydrogen bonds with backbone carbonyls, reproducing the capping motif of larger polyalanine helices. This is confirmed by comparison with Ac-Phe-(Ala)5-LysH+, which forms a 310 helix containing the same structural feature. In both molecules, we identified the vibrational bands of the N- and C-terminal amide NH stretches, which lack strong hydrogen bonds with carbonyls and consequently appear in a characteristic region above 3400 cm?1. A similar pattern is also present in the even longer peptide Ac-Phe-(Ala)10-LysH+, illustrating the generality of this capping motif. The two longer peptides contain additional, characteristic amide NH stretch bands below 3400 cm?1, which form the core of the helix.


Published in:
Journal of Physical Chemistry Letters, 6, 1504
Year:
2015
Publisher:
Washington, Amer Chemical Soc
ISSN:
1948-7185
Keywords:
Laboratories:




 Record created 2015-04-10, last modified 2018-09-13


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