Fig. 8. Frequency of Pgp residues interacting with ligands. The normalized interaction frequencies of Pgp's binding residues for all binding modes predicted of 4 representative compounds are shown (data for the other compounds are shown in Fig. S14†). The residues are considered to interact with the ligand if their heavy atoms are within 4 Å. The orange arrows point to the regions of the protein showing differences in their interaction patterns for different classes of compounds. High-affinity modulators like zosuquidar display the highest interaction frequencies with the binding residues pointing to a more specific mode of their binding.