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Time-resolved infrared spectroscopy of thiopeptide isomerization and hydrogen-bond breaking


Cervetto, V; Pfister, R; Helbing, J (2008). Time-resolved infrared spectroscopy of thiopeptide isomerization and hydrogen-bond breaking. Journal of Physical Chemistry. B, 112(11):3540-3544.

Abstract

The photoisomerization of the protected tetrathioxopeptide Boc-Ala-Gly(=S)-Ala-Aib-OMe was followed using time-resolved infrared spectroscopy in the amide I region in combination with isotope labeling. In acetonitrile at room temperature, approximately half of the molecules are found in a loop conformation, restrained by an intramolecular hydrogen bond, while the other half adopts more extended conformations. UV-excitation of the thioxopeptide unit immediately weakens the intramolecular hydrogen bond. After the molecules have relaxed to the electronic ground state with a 130 ps time-constant, a delayed re-formation of the intramolecular hydrogen bond is observed for molecules returning to the initial trans conformation of the thioamide bond, while the loop structure is permanently broken when the molecules isomerize to the cis conformation.

Abstract

The photoisomerization of the protected tetrathioxopeptide Boc-Ala-Gly(=S)-Ala-Aib-OMe was followed using time-resolved infrared spectroscopy in the amide I region in combination with isotope labeling. In acetonitrile at room temperature, approximately half of the molecules are found in a loop conformation, restrained by an intramolecular hydrogen bond, while the other half adopts more extended conformations. UV-excitation of the thioxopeptide unit immediately weakens the intramolecular hydrogen bond. After the molecules have relaxed to the electronic ground state with a 130 ps time-constant, a delayed re-formation of the intramolecular hydrogen bond is observed for molecules returning to the initial trans conformation of the thioamide bond, while the loop structure is permanently broken when the molecules isomerize to the cis conformation.

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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
Language:English
Date:20 March 2008
Deposited On:15 Jan 2009 13:39
Last Modified:18 Feb 2018 10:19
Publisher:American Chemical Society
ISSN:1520-5207
OA Status:Closed
Publisher DOI:https://doi.org/10.1021/jp710611n
PubMed ID:18293962

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