FIGURE 1.

Schematic picture of the model for the experimental setup used in the manipulation of RNA molecules. We show the configurational variables of the system x_b, i.e., x_r, x_h1, and x_h2, which are the extensions of each element (trapped bead, RNA molecule, and handles, respectively) along the reaction coordinate axis (i.e., the axis along which the force is applied). X_T is the end-to-end distance of the whole system, i.e., the distance between the center of the optical trap and the tip of the micropipette. The optical potential is well described by a harmonic potential of a one-dimensional spring of stiffness ɛ_b and equilibrium position at x_b = 0.