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Spectroscopy: An International Journal
Volume 27 (2012), Article ID 102423, 8 pages
http://dx.doi.org/10.1155/2012/102423

Impact of β-Turn Sequence on β-Hairpin Dynamics Studied with Infrared-Detected Temperature Jump

1Department of Biophysical Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
2Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor Street, Chicago, IL 60607-7061, USA

Copyright © 2012 Alexander Popp et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Folding dynamics for β-structure loss and disordered structure gain were studied in a model β-hairpin peptide based on Cochran’s tryptophan zipper peptide Trpzip2, but with an altered Thr-Gly (TG) turn sequence, that is, SWTWETGKWTWK, using laser-induced temperature-jump (T-jump) kinetics with IR detection. As has been shown previously, the TG turn sequence reduces the thermodynamic β-hairpin stability as compared to the Asn-Gly sequence used in Trpzip2 (TZ2-NG). In this study, we found that the TG-turn slows down the overall relaxation dynamics as compared to TZ2-NG, which were studied at higher temperatures where the time constants show little difference between relaxation of the β-strand and the disordered conformation. These time constants become equivalent at lower temperatures for TZ2-TG than was seen for TZ2-NG. The correlation of thermodynamic stability and rates of relaxation suggests that the change from NG to TG turn results in a slowing of folding, lower kf, with less change of the unfolding rate, ku, assuming two state behavior at higher temperatures.