Calorimetric Study of Maxima Hemocyanin Isoforms.

The thermal unfolding of hemocyanin isoforms, -HaH and -HaH, isolated from the hemolymph of garden snails maxima, was studied by means of differential scanning calorimetry (DSC). One transition, with an apparent transition temperature ( ) at 79.88°C, was detected in the thermogram of -HaH in 20 mM HEPES buffer, containing 0.1 M NaCl, 5 mM CaCl and 5 mM MgCl, pH 7.0, at scan rate of 1.0°C min. By means of successive annealing procedure, two individual transitions were identified in the thermogram of -HaH. Denaturation of both hemocyanins was found to be an irreversible process. The scan-rate dependence of the calorimetric profiles indicated that the thermal unfolding of investigated hemocyanins was kinetically controlled. The thermal denaturation of the isoforms -HaH and -HaH was described by the two-state irreversible model, and parameters of the Arrhenius equation were calculated.