In the tutorial of RNAfold it states,
RNAfold reads RNA sequences from stdin, calculates their minimum free energy (MFE) structure, prints the MFE structure in dot-bracket notation and its free energy to stdout.
In the example using the
-p --MEA options, the
- MFE = -5.00 and the
- ensemble Free Energy = -5.72.
How can the free energy of the ensemble be lower than the minimum free energy?