Figure 9.

The GdmHCl-denaturation thermodynamical parameters at pH 7 as monitored by the change in ellipticity at 222 nm in the far-UV CD spectra. (A) Temperature dependence of the m-value from CD measurements. Errors bars are fitting errors to the LEM equation. (B) The temperature dependence of the [GdmHCl]_1/2 (left axis, open squares) and ΔG (right axis, filled squares) values. The error bars are fitting errors to the LEM equation. The errors are larger at the higher temperatures, because the native baselines were shorter. The solid line represents the nonlinear least square fit of the data to , which is similar to Equation 7 except that here T₀, the reference temperature, was taken as 298 K. The use of this equation avoids a bias in the fitting due to the larger number of experimental data around the thermal midpoint. From this equation, the ΔH_m, T_m, and ΔC_p can be easily obtained. The experimental data at the T_m (right side of figure) were obtained from CD thermal denaturation experiments. ΔG values were obtained by using the mean m-value over all the temperatures. The temperature-dependence of ΔG was consistent with a temperature-independent heat capacity change, ΔC_p, of 1.14 ± 0.06 kcal mol⁻¹ K⁻¹.