Fig. 1.

(A) Adjacency in an RNA folding landscape is encoded by insertion or deletion of a single base pair. The underlying graph of an RNA folding landscape is connected owing to the existence of the particular valid secondary structure that contains no base pair (open structure). (B) Schematics representation of an energy landscape and its associated barrier tree. Local minima are labeled with numbers (1–5), saddle points with lowercase letters (a–d). The global minimum is marked with an asterisk