The thermodynamic parameters for the process of protein unfolding can be obtained through differential scanning calorimetry. However, the unfolding process may not be a two state one. Between the native and the unfolded state there may be association or dissociation processes or the formation of an intermediate state. As a consequence of this, the interpretation of the calorimetric data can not be straightforward. In this work we present two general models for the unfolding process of an oligomeric protein in which an intermediate state, N or In is present:
In model I, the first step represents the dissociation of the oligomer into the monomeric native species and the second step represents the denaturation process. In model II the first step represents the conformational change of the oligomer and the second step the dissociation of this species with the concomitant unfolding process. A canonical ensemble was employed to describe these systems, considering that the total protein concentration remains constant.
In the present work we show and analyze the behaviour of these systems in different conditions, and how could this analysis help with the identification of the unfolding mechanism experimentally observed.
