Fig. 6.

Stability curves TCEO (• and ▪) and ECTO (○ and □) compared with the stability curves of T. thermophilus (broken line) and E. coli RNases H (dotted line) (Hollien and Marqusee 1999b). Each circle corresponds to a ΔG obtained from a guanidine denaturation experiment. Squares correspond to ΔGs obtained from temperature denaturation experiments. The dash-dot plot represents the constrained fit of TCEO stability data to the Gibbs-Helmholtz equation, in which ΔCp is fixed at 2.2 kcal mole⁻¹ K⁻¹. Fitting the stability curves to Gibbs-Helmholtz equation (without any constraints) results in ΔCp of 1.6 ± 0.2 kcal mole^–1 K⁻¹, Tm of 76 ± 1°C, and ΔH of 68 ± 2 kcal for TCEO; and ΔCp of 2.4 ± 0.3 kcal mole⁻¹ K⁻¹, Tm of 61 ± 1°C, and ΔH of 89 ± 2 kcal for TCEO.