A test of the linear extrapolation of unfolding free energy changes over an extended denaturant concentration range

Guanidine hydrochloride (GdnHCl) and thermally induced unfolding measurements on the oxidized form of Escherichia coli thioredoxin at pH 7 were combined for the purpose of assessing the functional dependence of unfolding free energy changes on denaturant concentration over an extended GdnHCl concentration range. Conventional analysis of GdnHCl unfolding exhibits a linear plot of unfolding ΔG vs [GdnHCl] in the transition zone