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


Oppermann, Malte; Spekowius, Jasmin; Bauer, Benjamin; Pfister, Rolf; Chergui, Majed; Helbing, Jan (2019). Broad-Band Ultraviolet CD Spectroscopy of Ultrafast Peptide Backbone Conformational Dynamics. Journal of Physical Chemistry Letters, 10(11):2700-2705.

Abstract

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 spectroscopy is possible in combination with site-selective thio substitution in peptides and proteins.

Abstract

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 spectroscopy is possible in combination with site-selective thio substitution in peptides and proteins.

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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
Uncontrolled Keywords:Ultrafast Spectroscopy Circular Dichroism Peptides Thioamides
Language:English
Date:6 June 2019
Deposited On:08 Aug 2019 09:40
Last Modified:08 Aug 2019 09:40
Publisher:American Chemical Society (ACS)
ISSN:1948-7185
OA Status:Closed
Publisher DOI:https://doi.org/10.1021/acs.jpclett.9b01253
Official URL:https://pubs.acs.org/doi/10.1021/acs.jpclett.9b01253
Project Information:
  • : FunderSNSF
  • : Grant ID200021_169742
  • : Project TitleProbing local peptide structure and dynamics with UV labels and non-linear spectroscopy

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Embargo till: 2020-06-05