Note that the aforementioned residues in the selectivity filter and outer-ring have negative contributions to the projected electric field in the pore. This means that they exert an electric field that is pointing up. This is because they are located above our two probes, and they exert an attractive force that brings Na + from the central cavity to the region above the selectiv- ity filter. In parallel, we see positive contributions from Gln-360, Tyr-362, Arg-922, and Tyr-1755, suggesting that these residues facilitate the motion of Na + down the central cavity, assisting permeation through the pore. Our calculations also reveal that the membrane lipids, as well as Na + and Cl -, have significant positive contribution to the projected electric field in the pore, assisting permeation. Meanwhile, water facilitate the motion of Na + upwards, where it interact with the residues in the selectivity filter and outer-ring. Therefore, the sign of the projection compared to the location of the probes enables the identification of residues that assist Na + binding to the selectivity filter or Na + permeation.