Figure 6.

Van' t Hoff plots showing the effects of temperature on the disorder↔order equilibrium in the thick filament. Values of $K_{\text{ord}}^{\text{app}}$ were obtained in the presence of MgATP (solid squares), MgATP+blebbistatin (open squares), and MgADP+blebbistatin (open circles). The lines are results of curve-fitting to the van' t Hoff equations (see Eq. 2). For MgATP and in the absence of blebbistatin, the enthalpy changes were determined to be ΔH_AB = −144 kJ/mol, and ΔH_BC = 116 kJ/mol. These values are similar to those previously obtained with a series of nucleotide ligands (3). For conditions that contained blebbistatin, ΔH_AB = −181 kJ/mol and ΔH_BC = 111 kJ/mol. The best fit values for ΔS_AB and ΔS_BC are shown in Table 1.