Experimental Study of Dynamic Specific Heat Capacity of Protein Aqueous Solutions

Abstract

We performed the measurements of the dynamic heat capacity of aqueous solutions of lysozyme and α-chymotrypsin near heat denaturation by using an ac calorimeter. The obtained values of the ac enthalpy and the ac entropy at the heat denaturation process were much smaller than those measured by usual dc calorimeters. This fact tells us that the main part of the dynamic denaturation process takes place at a frequency lower than our measuring frequency of 0.6 Hz, in consistent with the results given by T-jump experiments. Furthermore, it was clarified by a circular dichroism measurement that the disulfide bridges play an important role in holding the three-dimensional structure of the proteins.