Fig 7. Two-ion permeation for Na⁺ in the Na_v1.2 SF with protonated Lys⁺.

2D free energy projections showing the 2-ion conduction mechanism for: a) the bottom ion and Lys; b) the two ions and Lys; and c) the two ions; where z₁ and z₂ correspond to the z positions of the bottom and top ions, z₁₂ the z position of the COM of the two ions, and z_Lys the z position of the Lys⁺ ammonium group. Snapshots, with the DEKA ring in purple, EEDD ring in green, and the charged ammonium group of the Lys shown as blue and white balls, indicate the Na⁺ ion (orange balls) movements.