The temperature-dependence of the folding free energy ΔG°T for (a) NaCl and (b) MgCl2 solutions. (Solid lines) The TBI theory; (dotted lines) experimental data with the use of the equation ΔGT° = ΔH° − TΔS°, where ΔH° and ΔS° are taken from experiments. (a) The upper three lines are for sequence GGAATTCC at 0.046, 0.1, and 0.267 M NaCl (from the top to bottom) (79,80), and the bottom three lines are for sequence ATCGTCTGGA at 0.069, 0.22, and 0.62 M NaCl (from the top to bottom) (82). (b) The three lines are for sequence GCCAGTTAA at 1, 10, and 100 mM MgCl2 (from the top to bottom) (37).