Figure 3.

The energy landscapes F(n,nn) vs. Temperature T (in °C) for (A) mutant α mRNA fragment (Fig. 2c) and (B) E. coli 23S rRNA fragment (Fig. 2d). F(n,nn) is the free energy for a state with n native contacts and nn non-native contacts, where the native and non-native contacts are defined according to the native structure N. The free energies (in kcal/mol) are relative to the native states. Under native conditions, the number of non-native contacts need not equal zero, because loops can bump into the chain in ways that involve no stable contact. Stable states are valleys, highlighted by the symbols on the energy landscapes.