Detection of the voltage-sensing elements in ClC1 (Park and MacKinnon, 2018), muscarinic acetylcholine receptor M₂ (Haga et al., 2012) and Na⁺/K⁺ ATPase (Kanai et al., 2013). (A) Illustrated representation of the membrane proteins. The residues whose $ζ j$ value is larger than the detection threshold are shown. (B) $ζ j$ values estimated for ClC1, M₂ receptor, and Na⁺/K⁺ ATPase; the average and standard deviation are shown. The positively and negatively charged residues are shown as blue and red bars, respectively. The gray rectangles correspond to different regions of the proteins: B-R, the α-helical transmembrane segments in ClC1; TM1–TM7, the transmembrane segments in the M₂ receptor; TM1–TM10, the transmembrane segments in Na⁺/K⁺ ATPase; β and γ, auxiliary subunits of Na⁺/K⁺ ATPase.