  The branching of an RNA molecule is an important structural characteristic
yet difficult to predict correctly, especially for longer sequences. Using
plane trees as a combinatorial model for RNA folding, we consider the
thermodynamic cost, known as the barrier height, of transitioning between
branching configurations. Using branching skew as a coarse energy
approximation, we characterize various types of paths in the discrete
configuration landscape. In particular, we give sufficient conditions for a
path to have both minimal length and minimal branching skew. The proofs offer
some biological insights, notably the potential importance of both hairpin
stability and domain architecture to higher resolution RNA barrier height
analyses.
