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Broad-Band Ultraviolet CD Spectroscopy of Ultrafast Peptide Backbone Conformational Dynamics

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Oppermann Malte, Spekowius Jasmin, Bauer Benjamin, Pfister Rolf, Chergui Majed, Helbing Jan,
Project Probing local peptide structure and dynamics with UV labels and non-linear spectroscopy
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Original article (peer-reviewed)

Journal The Journal of Physical Chemistry Letters
Volume (Issue) 10(11)
Page(s) 2700 - 2705
Title of proceedings The Journal of Physical Chemistry Letters
DOI 10.1021/acs.jpclett.9b01253

Open Access

Type of Open Access Green OA Embargo (Freely available via Repository after an embargo)


The far-UV spectral window widely used for the conformational analysis of biomolecules is not easily covered with broad-band lasers. This has made it difficult to use circular dichroism (CD) spectroscopy to directly follow fast structure changes. By combining transient CD spectroscopy in the deep-UV with thioamide substitution, we demonstrate a method to overcome this difficulty. We investigated a dipeptide whose two carbonyl oxygen atoms were replaced by sulfur, red-shifting the strong lowest-lying ππ* transitions into the more accessible 250−370 nm spectral window. Coupling of the two thioamide units cannot be resolved by achiral 2D-UV spectroscopy, but it gives rise to a pronounced bisignate CD spectrum. The transient CD spectra reveal weakening of this coupling in the electronically excited state, where conformational constraints are released. Our results show that direct local probing of fast backbone conformational change via CD is possible in combination with site-selective thio substitution in peptides and proteins.