Differential scanning calorimetric study of the binding of the primary water of hydration to nucleosides

Differential scanning calorimetry was used to study the water of hydration of all of the nucleosides at 59% relative humidity. Hydration was observed in pristine samples of guanosine, (rG), deoxyguanosine, (dG), and deoxyadenosine, (dA). Two inequivalent water sites were observed in dG and one site in rG. Re-hydration was observed in rG and dG, but not in dA. The activation energies for rG were 0.697 +/- 0.051 eV and 0.683 +/- 0.090 eV for pristine and cycled samples respectively. dG had activation energies of 0.726 +/- 0.026 eV and 0.997 +/- 0.034 eV for the first and second peaks in the pristine samples while the activation energy for cycled dG was 0.671 +/- 0.133 eV.