Binding of bupivacaine is localized to the central pore cavity . (A–E) The pore binding mode of bupivacaine in neutral (A and C) versus protonated (B and D) form – showing the free energy surfaces (FES) reproduced from metadynamics simulations (A and B); representative binding pose of each of the top five clusters (C and D); percentage of the top five clusters where interactions between the mexiletine and protein residues were identified (E). FES contours are shown every 4 kJ/mol.