The effect of temperature on the oxidation-reduction potential of the diphosphopyridine nucleotide system.

A number of investigators have estimated the oxidationreduction potential of the diphosphopyridine nucleotide (DPN) system from equilibrium and thermal data (l-4). These data were obtained at several different temperatures ranging from 25-38”. Therefore, the results are not strictly comparable. The potential of the DPN system at 30” has been measured in this laboratory by potentiometric techniques (5). In order to compare the potentials determined at different temperatures and to calculate the standard enthalpy change for the reduction of DPN+, the temperature coefficient of the potentials of the DPN system has been measured and calculated for two standard states.