Stabilizing helical peptides with negative polarity or charge: capping with cysteine

Document Type

Article

Publication Title

Journal of Physical Chemistry B

Department

Chemistry

ISSN

1520-6106

Volume

112

Issue

18

DOI

10.1021/jp073315a

First Page

5702

Last Page

5709

Publication Date

4-17-2008

Abstract

Alanine-based peptides are widely known for their propensity to form helices, whether in the gas phase or in aqueous solution. Interactions of substituent groups or peptides with the helical macrodipole may either encourage or discourage the formation or stability of a helix, depending upon the placement of these groups. We report the first study of the inductive stabilization of a number of peptides through electronegative or anionic N-terminal residue capping. Using Charmm27/CMAP equilibrium and replica-exchange (REX) molecular dynamics (MD) simulations with Generalized Born implicit solvation methods, we find that the N-terminal cysteine capping of alanine peptides strongly enhances the helicity, even allowing the helical moiety to remain at temperatures beyond the denaturing temperature. Though the overall number of hydrogen bonds is enhanced, this stabilization seems to occur indirectly through interaction with the helical macrodipole rather than as a direct result of hydrogen bonding involving the cysteine, though the nature of the hydrogen bonding changes.

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