Correlations of ligand-interaction energies (U values) using molecular docking with P450s 2A13 4EJG (nicotine-type) and 4EJH (NNK-type) with 24 chemicals used in this study and NNK, indole, pilocarpine, nicotine, and coumarin. These latter five chemicals indicated with blue squares and naphthalene, phenanthrene, and biphenyl are marked with red squares (Figure 8A). Effects of spectral binding intensities (ΔAmax/Ks ratio) on ligand binding energies (U values) using P450 2A13 4EJG (nicotine-type) (Figure 8B).