Correlation of ligand-interaction energy obtained with P450 2A13 4EJG (nicotine-type) and P450 2A13 2P85 (indole-type) (A), P450 2A13 4EJH (NNK-type) and P450 2A6 1Z10 (coumarin-type) (B), P450 2A13 4EJH (NNK-type) and P450 2A6 4EJJ (nicotine-type) (C), P450 2A13 4EJG (nicotine-type) and P450 2A6 4EJJ (nicotine-type) (D), P450 2A6 1Z10 (coumarin-type) and P450 2A6 4EJJ (nicotine-type) (E), and P450 2A6 4EJJ (coumarin-type) and P450 2A6 3T3R (pilocarpine-type).