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Updated: Jun 25, 2026

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors
Published on: April 27, 2017
Urea, but not guanidinium, destabilizes proteins by forming hydrogen bonds to the peptide group
Woon Ki Lim1, Jörg Rösgen, S Walter Englander
1Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Abstract:
The mechanism by which urea and guanidinium destabilize protein structure is controversial. We tested the possibility that these denaturants form hydrogen bonds with peptide groups by measuring their ability to block acid- and base-catalyzed peptide hydrogen exchange. The peptide hydrogen bonding found appears sufficient to explain the thermodynamic denaturing effect of urea. Results for guanidinium, however, are contrary to the expectation that it might H-bond. Evidently, urea and guanidinium, although structurally similar, denature proteins by different mechanisms.
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