ANALYSIS OF DIFFERENTIAL SCANNING CALORIMETRY DATA FOR PROTEINS - CRITERIA OF VALIDITY OF ONE-STEP MECHANISM OF IRREVERSIBLE PROTEIN DENATURATION

We consider in this work the analysis of the excess heat capacity C-p( ex) versus temperature profiles in terms of a model of thermal protein denaturation involving one irreversible step. It is shown that the de pendences of In C-p(ex) on 1/T (T is the absolute temperature) obtaine d at various temperature scanning rates have the same form. Several ne w methods for estimation of parameters of the Arrhenius equation are e xplored. These new methods are based on the fitting of theoretical equ ations to the experimental heat capacity data, as well as on the analy sis of the dependence d(ln C-p(ex))/d(1/T) on 1/T. We have applied the proposed methods to calorimetric data corresponding to the irreversib le thermal denaturation of Torpedo californica acetylcholinesterase, c ellulase from Streptomyces halstedii JM8, and lentil lectin. Criteria of validity for the one-step irreversible denaturation model are discu ssed. (C) 1997 Elsevier Science B.V.