The enthalpy of hydrolysis of various 3',5'-and 2',3'-cyclic nucleotides.

The enthalpy of hydrolysis of the 3’-bond of several cyclic 3’,5’-nucleotides and of the 2’-bond of several cyclic 2’,3’nucleotides has been measured calorimetrically. In each case, the enthalpy was indicative of a high energy bond, although values for different compounds varied from -7.7 to 14.1 kcal mole-‘. The enthalpy of hydrolysis of the cyclic 3’,5’-nucleotides, but not that of the cyclic 2’,3’-nucleotides, was markedly affected by the nature of the base.