Prior studies using static QM methods also delineated metastable substates of a motor very similar to the present Motor S . Although the conformations of those substates are similar to the ones reported here, the prior studies proposed a different pathway to the stable form. Rather than going through the relatively high energy MS1 as found here, their pathway goes to the stable form through the lower energy MS2. Potential explanations for the difference between the prior results and those presented here include the fact that the motor molecule studied previously had an extra methoxy group, relative to Motor S; the prior studies' use of high-level QM calculations throughout; the challenge of finding all relevant transition states by QM geometric optimization in the prior approach; and our use of a dynamical, rather than a static, method.