Fig. 9
The probabilities ρ (black) and ρ∗ (blue) for structure neighbors of Phenylalanine. Fifty thousand inverse folds of Phenylalanine were used to compute these probabilities. Both axes are scaled logarithmically. The rank 1 structure, the structure into which Phenylalanine is most likely to mutate, either freely (black curve) or quasineutrally (blue curve) is the same for the two curves. However the probability to mutate quasineutrally to this structure, ρ∗, is 29 times higher than its free probability ρ. This explains why in free simulations, at the time of a transition the population splits between different neutral networks, whereas for quasineutral ones the transition is rapid and without much splitting