Our chosen test system consists of a valinealanine dipeptide, explicitly solvated in water. We chose to focus our tests on a simple dipeptide because this minimizes backbone motions and reduces the possibility of the sidechains interacting with one another, which could make sampling more challenging and complicate validation or conflate sampling challenges with implementation errors. Alanine dipeptide is a commonly used model system for molecular simulations; however the absence of rotatable bonds involving central heavy atoms in the alanine sidechain makes it unsuited for our purposes. The next simplest dipeptide option is valine-alanine, which possesses a single significant rotatable bond in the valine sidechain that has 3 distinct rotamers as shown in Figure . Initially a valine-valine system was tested, but there were challenges associated with controlling for the interdependence and influence of one residue's rotamer state on the other when generating reference results for comparison with BLUES (data not shown). A valine-glycine system was also explored, however the absence of a glycine sidechain resulted in the dipeptide backbone collapsing on itself.