Dehydration of cytosine monohydrate at physiological temperatures.

Neutron diffraction, thermogravimetric, and mass spectrographic measurements have been used to show that cytosine monohydrate loses its water of hydration at physiological temperatures (approximately equal to 37 degrees C) and converts to cytosine. The "activation energy" for the dehydration process has been determined from isothermal weight curves and is 27.1 +/- 0.6 kcal . mol-1. It is suggested that pyrimidine dehydration may be involved in structural changes in DNA.