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Updated: Mar 8, 2026

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors
Published on: April 27, 2017
Do guanidinium and tetrapropylammonium ions specifically interact with aromatic amino acid side chains?
Bei Ding1,2, Debopreeti Mukherjee1, Jianxin Chen1,2
1Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104.
Abstract:
Many ions are known to affect the activity, stability, and structural integrity of proteins. Although this effect can be generally attributed to ion-induced changes in forces that govern protein folding, delineating the underlying mechanism of action still remains challenging because it requires assessment of all relevant interactions, such as ion-protein, ion-water, and ion-ion interactions. Herein, we use two unnatural aromatic amino acids and several spectroscopic techniques to examine whether guanidinium chloride, one of the most commonly used protein denaturants, and tetrapropylammonium chloride can specifically interact with aromatic side chains. Our results show that tetrapropylammonium, but not guanidinium, can preferentially accumulate around aromatic residues and that tetrapropylammonium undergoes a transition at ∼1.3 M to form aggregates. We find that similar to ionic micelles, on one hand, such aggregates can disrupt native hydrophobic interactions, and on the other hand, they can promote α-helix formation in certain peptides.
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