The Advanced Photon Source (APS) selected structures of cytochrome P450 2E1 for a highlight in their annual report. The structure shown in yellow is CYP2E1 with indazole (yellow sticks) in the active site and the yellow mesh indicating two small voids, one of which is the constrained active site cavity. The structure shown in blue is the same CYP2E1 enzyme with an imidazolyl fatty acid (blue sticks) in the active site with the corresponding mesh indicating again representing the active site cavity, which in this case is significantly expanded by merging the two voids in the indazole structure. The primary difference between the two structures is the position of Phe298, also shown in sticks.