The effect of pH was characterised on the thermal stability of magnesium saturated skeletal and cardiac α-actin isoforms with
differential scanning calorimetry (DSC) at pH 7.0 and 8.0. The calorimetric curves were further analysed to calculate the
enthalpy and transition entropy changes. The activation energy was also determined to describe the energy consumption of the
initiation of the thermal denaturation process. Although the difference in Tmvalues is too small to interpret the difference between the a-actin isoforms, the values of the activation energy indicated
that the α-skeletal actin is probably more stable compared to the α-cardiac actin. The difference in the activation energies
indicated that lowering the pH can produce a more stable protein matrix in both cases of the isoforms. The larger range of
the difference in the values of the activation energies suggested that the α-cardiac actin is probably more sensitive to the
change of the pH compared to the α -skeletal actin.