Figure 5.

Free energy of formation of the RNA hairpin as a function of [Mon⁺]. Main panel: free energy obtained experimentally (squares), using the logarithmic dependence with salt concentration given by g₁([Mon⁺]) (dashed line) and using the TBI model (continuous line) Inset: persistence lengths P obtained from the application of the Thick Chain model to published experimental data for poly-U RNA stretching in buffers containing 5, 10, 50, 100, 300 and 500 mM of [Na⁺] (squares) (69,70). We have included the value of the persistence length P that we obtained in this study at 1050 mM [Mon⁺] (empty circle). Two different fits to data were done from Equation 15: a fixed value ν = 1 (red) and ν as free parameter ν = 0.60±0.06 (blue).