Investigation of the Heat Capacities of Proteins by Statistical Mechanical Methods

Abstract

In this study, the additional heat capacity which appear during the water dissociation of the proteins that are one of the soft materials, have been considered by the statistical mechanical methods. For this purpose, taking the electric field E and total dipole moment M as the thermodynamical variables and starting with the first law of thermodynamics an equation which reveals the thermodynamical relation between the additional heat capacity in effective electric field and the additional heat capacity at the constant total dipole moment, has been obtained. It is found that, the difference between the heat capacities depends linearly on the temperature. To bring up the hydration effect during the folding and unfolding of the proteins the physical properties of the apolar dissociation have been used. In the model used for this purpose; the folding and unfolding of the proteins in the formed electric field medium have been established on this basis. In this study with the purpose of revealing the additional effect to the heat capacity, the partition functions for the proteins which have been calculated in single protein molecule approach by A. Bakk, J.S. Hoye and A. Hansen; Physica A, 304, (2002), 355-361 have been taken in order to obtain the free energy. In this way, the additional free energy has been related to the heat capacities. By calculating the heat capacity in the effective electric field theoretically and taking the heat capacity at constant total dipole moment from the experimental data, the outcomes of the performed calculations have been investigated for Myoglobin and other proteins.