The diagram in Figure offers a kinetic model of Motor S and includes estimated rate constants for many of the interstate conversions. Although we do not have estimated rate constants for photoisomerization of the stable form into the various metastable substates (orange arrows), the properties of the motor may be explored by assuming a range of values for these missing quantities and solving for the steady state probabilities and rates, as detailed in the Appendix A. (The Appendix also considers the consequences of backward photoisomerization from the metastable to the stable form, which is omitted here.) The present results correspond to experiments where the motor is continuously illuminated while at a temperature that allows THI , so that the motor may rotate continuously.