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Folding and unfolding of the tryptophan zipper in the presence of two thioamide substitutions

Citation

Helbing, Jan; Spekowius, Jasmin; Pfister, Rolf (2021), Folding and unfolding of the tryptophan zipper in the presence of two thioamide substitutions, Dryad, Dataset, https://doi.org/10.5061/dryad.4tmpg4f9r

Abstract

We studied the stability and folding and unfolding kinetics of the tryptophan zipper, containing dierent 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 photo-switching, reflecting a local change in coupling and geometry.

Methods

See methods section of the paper and supporting information.

Usage Notes

ReadMe files describe the data structure organized by the figure number in the paper and the different sections of the SI. Data files can be associated by their name: filenames start with the figure number (or SI section), followed the experiment (trUV for transient UV, trIR for transient IR, sCD for static CD, UVvis for uv-visible absorption, MS for mass spectrum, NMR for nuclear magnetic resonance), date of acquisition and sample name. Further information at the end of the filename permits unique identification. Pdf files of mass spectra (SI section 2) contain explanations.

Funding

Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Award: 200020_192240

Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Award: 200021_169742

Universität Zürich