Figure 2.

(Left) The folding free energy of a stem-loop site-specifically attached to a C6OH SAM-on-gold surface is more sensitive to ionic strength than that of the same stem-loop in solution. This is because attachment to this negatively charged (at the potential applied in our experiments) surface destabilizes the folded state through electrostatic repulsion.⁵ (Right) This scheme serves to illustrate the dimensions of the stem loop relative to the potential field that forms above the surface when a potential is applied. Specifically, shown are the electric fields produced if the surface is at a potential of 50 (red) or 150 mV (blue) (versus the potential of zero charge; pzc) at ionic strengths of 25 (dashed lines) or 250 mM (solid lines). At low surface charge and/or high ionic strength the electric field experienced by the stem-loop is minimal. The left-hand panel was adapted from ref 5.