Interestingly, the maximal rotation rate (Figure ) does not depend dramatically on the ratio of metastable substates immediately following photoisomerization. Assuming that photoisomerization generates only MS1 (MS1:MS2:MS3:MS4=1:0:0:0) increases maximal rotation rate by about 10% (Fig 9B ), because MS1 is close to completing THI ( . Conversely, assuming that photoisomerization generates only MS2 (MS1:MS2:MS3:MS4=0:1:0:0) reduces maximal rotation rate by about 15%, because MS2 must go through a relatively slow conversion to MS3 before going to MS1 and then to stable form (Fig ). The insensitivity of the rotation rate to the details of photoisomerization supports the approach taken in this study, which focuses on THI process with less comprehensive modeling of photoisomerization. However, the rotation rates of other light-driven motors may not be so insensitive to the distribution of metastable substates generated by photoisomerization. For example, if a motor had the same transition network and time constants as in Fig 7 for a much longer time constant to go from MS1 to MS3, its rotation rate would be more sensitive to the distribution of metastable substates generated by photoisomerization, as shown in Figure .