Na⁺ binding and permeation pattern in the pore domain of TRPV1. (A) The contour plot of Na⁺ density on the R-z plane around TRPV1. (B) Side view of the three-dimensional Na⁺ density map. Only two subunits are shown for clarity. The ion density is shown as the magenta isosurface. The binding sites and key residues are labeled. The density threshold used to plot the sodium isosurface is 0.1 Å⁻³. (C) Evolution of the z coordinates of permeating Na⁺ through the TRPV1 channel. The boundaries of the narrow pore region are indicated by dashed lines. The z coordinates of each Na⁺ are shown in different colors.