Enthalpy of Unfolding (ΔH)
Circular Dichroism (CD) , Thermal Denaturation
0.1 M sodium cacodylate-HCl, 2.5 M GdmCl
Thermal unfolding transitions of 4 μM protein in 0.1 M sodium cacodylate-HCl (pH 7.0), 2.5 M GdmCl were followed by circular dichroism spectroscopy at 222.6 nm with a 1 nm bandwidth in 10 mm cells using a Jasco J-600 spectropolarimeter equipped with a PTC-348 WI Peltier device. The data were analyzed according to a two-state model using non-linear regression and the program Grafit (Erithacus Software, Staines, UK), the heat capacity change ΔCp was held constant at 4000 J mol-1 K-1. The reversibility of thermal unfolding was ascertained by measuring a second transition after cooling to the starting temperature.