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Charge‐Induced Unzipping of Isolated Proteins to a Defined Secondary Structure
Author(s) -
González Flórez Ana Isabel,
Mucha Eike,
Ahn DooSik,
Gewinner Sandy,
Schöllkopf Wieland,
Pagel Kevin,
von Helden Gert
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201510983
Subject(s) - protein secondary structure , chemistry , charge (physics) , chemical physics , amide , crystallography , protein structure , charge density , computational chemistry , physics , organic chemistry , quantum mechanics , biochemistry
Here we present a combined experimental and theoretical study on the secondary structure of isolated proteins as a function of charge state. In infrared spectra of the proteins ubiquitin and cytochrome c, amide I (C=O stretch) and amide II (N–H bend) bands can be found at positions that are typical for condensed‐phase proteins. For high charge states a new band appears, substantially red‐shifted from the amide II band observed at lower charge states. The observations are interpreted in terms of Coulomb‐driven transitions in secondary structures from mostly helical to extended C 5 ‐type hydrogen‐bonded structures. Support for this interpretation comes from simple energy considerations as well as from quantum chemical calculations on model peptides. This transition in secondary structure is most likely universal for isolated proteins that occur in mass spectrometric experiments.