Fig. S8.

Probabilities of backward steps relative to forward steps can be estimated using statistics from stepping experiments (data shown from ref. 16). The area under the curve for steps below and above 0° corresponds to forward and backward step probabilities, respectively. The areas on either side are calculated as highlighted in gray. Curves are truncated where each shows a second peak, corresponding to two steps being blurred together due to limitations in experimental resolution. The relative areas calculated for the data above suggest that the probability of a backward step is 7.3%.