Per-residue local electric field response R^j values and response propensity ζ^j values estimated by using different electric fields for a range of systems. (A) $R j$ and $ζ j$ values estimated for the system with NavMs by using large electric fields (between −0.02 and 0.02 V/Å), small electric fields (between −0.005 and 0.005 V/Å), and TIP4P water (large electric fields). The left panels illustrate the average, and the right panels illustrate the standard deviation. Note that in all three cases, the average of $R j$ and $ζ j$ is almost identical. The error is similar for large electric fields and different water models but significantly larger for the small electric fields. (B) $R j$ and $ζ j$values estimated for Shaker, NavMs, Cx26, TRPV1, VDAC1, ClC1, M₂ receptor, Na⁺/K⁺ ATPase, GLIC, and TWIK-1. $R z j$⁠, $R x j$⁠, and $R y j$ are computed by using the z, x, and y components of the local electric field, respectively (the z axis is the membrane normal, and the direction of the electric field). The left panels illustrate the average, and the right panels illustrate the standard deviation. Based on these data, we chose 0.02 to be the detection threshold for R.