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Folding and Unfolding of the Tryptophan Zipper in the Presence of Two Thioamide Substitutions


Spekowius, Jasmin; Pfister, Rolf; Helbing, Jan (2021). Folding and Unfolding of the Tryptophan Zipper in the Presence of Two Thioamide Substitutions. Journal of Physical Chemistry B, 125(28):7662-7670.

Abstract

We studied the stability and folding and unfolding kinetics of the tryptophan zipper, containing different double thioamide subsitutions. Conformation change was triggered by photoisomerization of an integrated AMPP photoswitch in the turn region of the hairpin, and transient spectra were recorded in the deep UV and the mid-IR, covering the time window of the (un)folding transition from picoseconds to tens of microseconds. Thio-substitution of inward-pointing backbone carbonyls was found to strongly destabilize the β-hairpin structures, whereas molecules with two outward pointing thio-carbonyls showed similar or enhanced stability with respect to the unsubstituted sequence, which we attribute to stronger interstrand hydrogen bonding. Thiolation of the two Trp residues closest to the turn can even prevent the opening of the hairpin after cis–trans isomerization of the switch. The circular dichroism due to the two thioamide ππ* transitions is spectrally well-separated from the aromatic tryptophan signal. It changes upon photoswitching, reflecting a local change in coupling and geometry.

Abstract

We studied the stability and folding and unfolding kinetics of the tryptophan zipper, containing different double thioamide subsitutions. Conformation change was triggered by photoisomerization of an integrated AMPP photoswitch in the turn region of the hairpin, and transient spectra were recorded in the deep UV and the mid-IR, covering the time window of the (un)folding transition from picoseconds to tens of microseconds. Thio-substitution of inward-pointing backbone carbonyls was found to strongly destabilize the β-hairpin structures, whereas molecules with two outward pointing thio-carbonyls showed similar or enhanced stability with respect to the unsubstituted sequence, which we attribute to stronger interstrand hydrogen bonding. Thiolation of the two Trp residues closest to the turn can even prevent the opening of the hairpin after cis–trans isomerization of the switch. The circular dichroism due to the two thioamide ππ* transitions is spectrally well-separated from the aromatic tryptophan signal. It changes upon photoswitching, reflecting a local change in coupling and geometry.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Physical and Theoretical Chemistry
Physical Sciences > Surfaces, Coatings and Films
Physical Sciences > Materials Chemistry
Uncontrolled Keywords:Physical and Theoretical Chemistry, Materials Chemistry, Surfaces, Coatings and Films
Language:English
Date:22 July 2021
Deposited On:11 Aug 2021 08:16
Last Modified:26 Mar 2024 02:37
Publisher:American Chemical Society (ACS)
ISSN:1520-5207
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1021/acs.jpcb.1c03327
Official URL:https://pubs.acs.org/doi/10.1021/acs.jpcb.1c03327
Related URLs:https://doi.org/10.5061/dryad.4tmpg4f9r (Research Data)
Project Information:
  • : FunderSNSF
  • : Grant ID200020_192240
  • : Project TitleSite-specific probing of peptide conformational dynamics by transient CD spectroscopy in the deep ultraviolet
  • : FunderSNSF
  • : Grant ID200021_169742
  • : Project TitleProbing local peptide structure and dynamics with UV labels and non-linear spectroscopy
  • Content: Published Version
  • Licence: Creative Commons: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)