Protein stabilization and counteraction of denaturing effect of urea by glycine betaine.

The counteraction of the denaturing effect of urea by osmolytes has been one of the most studied problems of osmolyte action. However, the possibility of synergy in osmolyte mixtures has often been neglected. Here, we report synergy in the glycine betaine (GB)-urea mixture by using a model peptide. The results show that in the GB-urea mixture, GB acts as a stronger osmolyte and urea becomes a weaker denaturing agent. This is reflected by an increase in the exclusion of GB from the peptide surface and a decrease in interactions between the peptide and urea. The cause of this synergistic behaviour includes direct interactions between GB and urea through hydrogen bonding, van der Waals interactions between them and strengthening of hydrogen bonding network of water in the GB-urea mixture. The results obtained in this study provide insights into osmolyte induced counteraction of the denaturing effect of urea.