To preserve move reversibility, the collection of starting states must match the states considered in rotational move proposals (Figure ). Thus if, at the point of evaluation, the sidechain rotamer is within the pre-defined range of favorable states, an NCMC move is proposed to another favorable state; if not, no move is proposed and we follow up with another round of m MD steps (Figure ). Relatedly, if an NCMC move is executed and the resulting state (after relaxation) falls outside of the range of favorable states, the move is immediately rejected. This scenario arises because the physical rotation of the atoms occurs at the midpoint of the NCMC switching protocol; as the intermolecular interactions are turned back on, the sidechain atoms can move and sometimes fall outside of the acceptable range.