Mechanism of the formation of DNA triplex and effect of chemical modifications on its stability as studied by isothermal titration calorimetry.

The thermodynamic properties of DNA triplex formation with various single-stranded oligo-DNAs as well as mismatched sequences were investigated by isothermal titration calorimetry (ITC). For the triplex formation of perfectly matched sequences, enthalpy changes and dissociation constants were measured and their temperature-dependences suggest that conformational change of pyrimidine single-strand and the intermediate state(s) are involved in the triplex formation. Effects of mismatches and chemical modifications on stability and specificity of the triplex formation will also be discussed.