Role of co-solute in biomolecular stability: glucose, urea and the water structure.

We have studied the action of urea and glucose on the stability of DNAand micelles. We measured the melting temperature of aqueous solutionsof DNA with urea or glucose as a co-solute; we have also measured thechanges in the critical micelle concentrations (cmc) of Sodium DodecylSulfate and Triton X-100 by addition of urea and glucose. Ourexperimental results show that glucose increases the melting temperature ofDNA and decreases the cmc, while urea acts in the contrary direction. The effects of urea and glucose on the stability of DNA and micelles canbe explained by the weakening and enhancement of hydrophobicinteractions, respectively. These effects on hydrophobic interactions arediscussed in this paper.