Nucleic acid–solvent interactions: Temperature dependence of the heat of solution of thymine in water and ethanol

✍ Scribed by José Alvarez; Rodney Biltonen

• Publisher: Wiley (John Wiley & Sons)
• Year: 1973
• Tongue: English
• Weight: 780 KB
• Volume: 12
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1973.360120809

✦ Synopsis

The heats of solution of thymine in water and ethanol have been determined calorimetrically as a function of temperature. These data, along with solubility data, have been used to calculate the thermodynamic quantities (AGt, A H , , ASt and AC,,J associated with the transfer of thymine from ethanol to water. Since A S t = -2 cal/mole deg and ACp,t = 0, it has been concluded that hydrophobic bonding does not play an important role in the thermodynamic stability of nucleic acids.

However, large heat capacities of solution of thymine are observed in both solvents

( A C o p ~

= 45 f 4 cal/mole deg). This is explained in terms of temperature variation in the degree of solvent-solute hydrogen bonding. It is our proposal that the components of macromolecules (i.e., nucleic acid bases and amino acids) do not make all possible hydrogen bonds with the solvent in the vicinity of room temperature. Thus the thermodynamic contribution of hydrogen bonding to the stability of macromolecules in aqueous solution must be reassessed.