Figure 5.

Extent to which surface attachment alters folding free energy depends on both ionic strength and the charge on the surface. The previously described continuum model (solid lines) of these effects⁵ accurately predicts the change in folding free energy for the two less highly charged surfaces we have characterized. For the C11OH SAM surface (blue), however, which is estimated to be at a potential of −210 mV under the conditions employed here,¹⁹ the continuum model fails. A more detailed model that considers the discrete volume of ions (discrete ion model) corrects this error and accurately predicts the free energy of the stem-loop on this surface (dashed line).