Urea, but not guanidinium, destabilizes proteins by forming hydrogen bonds to the peptide group.
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.
Lim
Woon Ki
WK
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Rösgen
Jörg
J
Englander
S Walter
SW
D019791:Guanidine / Q000737:chemistry*; D006860:Hydrogen Bonding; D010455:Peptides / Q000737:chemistry*; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry*
D010455:Peptides; D011506:Proteins; D014508:Urea; D019791:Guanidine