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Updated: Aug 18, 2025

Facile Protocol for the Synthesis of Self-assembling Polyamine-based Peptide Amphiphiles PPAs and Related Biomaterials
Published on: June 25, 2018
Does Urea Preferentially Interact with Amide Moieties or Nonpolar Sidechains? A Question Answered Through a Judicious
Simisola Ajayi1, Iman Asakereh1, Hanieh Rezasoltani1
1Department of Chemistry, the, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
Abstract:
The transfer model suggests that urea unfolds proteins mainly by increasing the solubility of the amide backbone, probably through urea-induced increase in hydrogen bonding. Other studies suggest that urea addition increases the magnitude of solvent-solute van der Waals interactions, which increases the solubility of nonpolar sidechains. More recent analyses hypothesize that urea has a similar effect in increasing the solubility of backbone and sidechain groups. In this work, we compare the effects of urea addition on the solvation of amides and alkyl groups. At first, we study the effects of urea addition upon solvent hydrogen bonding acidity and basicity through the perturbation in the fluorescence spectrum of probes 1-AN and 1-DMAN. Our results demonstrate that the solvent's hydrogen bonding properties are minimally affected by urea addition. Subsequently, we show that urea addition does not perturb the intra-molecular hydrogen bonding in salicylic acid significantly. Finally, we investigate how urea preferentially interacts with amide and alkyl groups moieties in water by comparing the effects of urea addition upon the solubility of acetaminophen and 4-tertbutylphenol. We show that urea affects amide and t-butyl solubility (lowers the transfer free energy of both amide (backbone) and alkyl (sidechain) groups) in a similar fashion. In other words, preferential interaction of urea with both moieties contributes to protein denaturation.
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