Cold denaturation of ubiquitin

Temperature induced unfolding of bovine ubiquitin in solutions with differe nt concentrations of guanidinium hydrochloride (GdmCl) has been measured us ing differential scanning calorimetry. It has been shown that at high conce ntrations of GdmCl the ubiquitin molecule can undergo both heat and cold in duced denaturation. Analysis of the enthalpy of unfolding of ubiquitin in t he presence of GdmCl shows a good agreement with the thermodynamic denatura nt binding model. The unfolding Gibbs energy is found to change linearly wi th guanidine concentration up to zero denaturant concentration. (C) 1999 El sevier Science B.V. All rights reserved.