Perron cluster cluster analysis+ (PCCA+) was then used to separate the trajectory frames of the MSM into 4 clusters. Visual inspection of the resulting macrostate clusters from PCCA+ revealed that there were two clusters, each with a symmetry equivalent partner (Figure ). The populations estimated from the MSM show the populations of the symmetric states to be roughly equal, with 32±8% and 26±6% for the two symmetric binding modes corresponding to the crystallographic binding mode. The other binding mode showed 18±5% and 23±6% populations for the symmetric equivalents (SI Figure ). We find that timescales for binding mode interconversion are extremely slow, both from analyzing our long conventional MD simulation directly, and from the implied timescales of the MSM. Direct analysis of our long single 806 ns trajectory (Figure ) showed that certain binding mode transitions are quite rare.