On the Melting Transition of RNA

The secondary structure of RNA can undergo a phase transition from a designed native state to a branched molten-globule. This melting transition is continuous, neglecting excluded volume. We study the effect of excluded volume interactions in good solvent on the melting transition. First, we calculate the effect of a constant external tension on the melting transition in the ideal polymer case and then, in the context of Flory theory, equate the tension with what would be generated by excluded volume. We find that, with excluded volume, the continuous melting transition is still second order but with a different exponent.