Figure 4.

Thermodynamic and kinetic results from kinITC for ECthiM. (A) Thermodynamic results. The evolution with the temperature of the thermodynamic parameters of all steps in equations 1a,b was obtained with kinITC used with model #1. The figures for ΔG and ΔS refer to the complete reaction involving TPP binding and RNA folding. The figure for ΔH collects ΔH_Binding, ΔH_Folding (dashed curve) and ΔH_ITC = ΔH_Binding + ΔH_Folding shown in blue with the individual values obtained by normal use of ITC at five different temperatures (blue dots). Note the extremum of K_d reached at the temperature where ΔH_Binding = 0 in agreement with the Van't Hoff equation linking K_d(binding) and ΔH_Binding. This extremum is here a maximum because $\mathit{}\mathit{\Delta }{\text{C}}_{\text{P}}\left(\text{Binding}\right)=\partial \mathit{\Delta }{\mathit{H}}_{\text{Binding}}/\partial \mathit{T}$ is positive. The injection curves of the kinITC experiments at different temperatures and their fit are shown in Fig. SD-5C. (B) Kinetic results. The evolution with the temperature of all kinetic parameters in equations 1a,b was obtained with kinITC used with model #1. The activation energies and $\mathit{}\mathit{\Delta }{\text{H}}_{\text{on}}^{‡}\text{and}\mathit{}\mathit{\Delta }{\text{H}}_{\text{U}}^{‡}$ were obtained as adjustable parameters in kinITC, and $\mathit{}{\text{ΔH}}_{\text{on}}^{‡}$and $\mathit{}{\text{ΔH}}_{\text{U}}^{‡}$ were deduced from $\mathit{}\mathit{\Delta }{\text{H}}_{\text{Binding}}^0=\mathit{}\mathit{\Delta }{\text{H}}_{\text{on}}^{‡}–\mathit{}\mathit{\Delta }{\text{H}}_{\text{off}}^{‡}$ and $\mathit{}\mathit{\Delta }{\text{H}}_{\text{Folding}}^0=\mathit{}\mathit{\Delta }{\text{H}}_{\text{F}}^{‡}–\mathit{}\mathit{\Delta }{\text{H}}_{\text{U}}^{‡}$, respectively.