Figure 5. Thermodynamic cooperativity in folding intermediates.

Linking free energies between tertiary interactions, ΔΔG_link, calculated from double mutant cycles (see Extended Experimental Procedures and Figure S5A for details). ΔΔG_link < 0 indicates cooperativity between tertiary interactions. (A) Pairwise linking energies in WT RNA in native state (U to N; 5 mM Mg²⁺). (B) As in (A), for the intermediate state (U to I_C; 0.8 mM Mg²⁺). (C,D) Pairwise linking energies in the background of a third mutation (large letters). See Extended Experimental Procedures for details.