RESUMEN
Investigations into the energy pathways of biomolecular interactions by use of dynamic force spectroscopy are limited by the range of loading rates accessible with a single technique. In the work discussed in this paper, this range has been extended for a previously studied system by using the biomembrane force probe (BFP). This work builds on our previous single-molecule atomic force microscopy (AFM) study of the dissociation of a bulge-motif-containing RNA complex. The disparity observed, at high loading rates, between the dissociation of a 12-base pair complex with and without a central three-base pair bulge was not observed at low rates. This suggests that the two species share a similar outer barrier to dissociation and that inclusion of the bulge motif creates an additional barrier at a distance closer to the bound state. Experiments performed in different buffer environments yielded similar results. The results, when combined with those of previous studies, suggest that the shared outer barrier to dissociation is that due to a rearrangement and fraying of the ends of the helix.