We performed molecular docking calculations on molecules containing the ester group among the OECD list to verify similar binding conformations. Of the 4,730 PFASs in the OECD list, 414 have an ester functional group. Figure shows four different representative ester-containing molecules bound to CYP2C9. In particular, the ester-containing molecules in the OECD list bind strongly with Fe 2+ of the HEME group (an active site of Cyp enzyme), which is similar to the binding interactions that we observed in the CF dataset. Therefore, we expect a large portion of the 414 ester-containing molecules among the OECD list to form strong bonds with Fe 2+ of the HEME group with a similar conformation, leading to bioactivity toward Cyp enzymes. Furthermore, based on our docking calculations, 87.7% of these 414 molecules have a stronger binding affinity than -5 kcal/mol (the average binding affinity is -5.77 kcal/mol), which falls in the range of the mean binding affinity of the bioactive molecules from the CF dataset. We then clustered the OECD dataset into 40 clusters using the k-means clustering method.