Here, we define a transition as being a move of the valine χ 1 rotamer from one stable conformational state to another (eg. when χ 1 transitions from gauche(-) to trans or -60 • to ±180 • ). For this particular system, BLUES confers no advantage over classical MD (Figure ). There is no significant difference in the number of transitions per nanosecond of simulation time (1.9±0. respectively), but classical MD is significantly more efficient at sampling rotamer states by our metric of transitions per million force evaluations (2.3±0.4 vs 4.2±0.6 for BLUES and MD, respectively). As evidenced by the relatively high frequency of rotamer transitions for both BLUES and MD (Figure ), the valine sidechain in our valine-alanine system is one that is quite mobile and readily sampled by classical MD and thus is unlikely to benefit from methods that specifically enhance sidechain rotamer sampling at an added cost. From our umbrella sampling of the valine-alanine, we find that the maximum barrier to rotation of valine χ 1 is fairly low (6.5k B T ≈ 3.8 kcal/mol) and as such, is not a good test case for evaluating the potential benefits of BLUES when transition barriers are large.