Unbiased selection of features to describe chignolin for all force fields. Four different featurizations were tested for constructing MSMs: (1) distances, d, (2) inverse distances, d -1 , (3) backbone dihedral angles (ϕ, ψ), and (4) the combination of (ϕ, ψ) and d -1 . Featurizations were evaluated based on the average and standard deviation of VAMP-2 scores over 50 iterations (Figure ), where each iteration is an independent 50:50 split of training and testing data. These results show that for most force fields, inverse distance featurizations have a higher average VAMP-2 score than distances alone. (The exceptions are for AMBER99SB and AMBER99SB-ildn, which show differences within standard deviation.) With few exceptions (which were also within standard deviation), backbone dihedral (ϕ, ψ) featurizations produced the lowest VAMP-2 scores.