Figure 4.

Effective channel closure by voltages ≤50 mV requires a threshold gate radius for conduction. (A) G/V relations of the full-channel model on a semi-logarithmic scale. (Solid line) Conduction is abolished at gate radii r < 0.2 nm regardless of presence of liquid water in the pore. (Dashed line) Conduction is controlled by the probability that the gate is water-filled, P₁ (compare Eq. 1). (Dotted line) Reducing VS-gate coupling energy (see text) degrades channel closure by hyperpolarization. (B) The exponential region of the G/V relation is associated with a near-asymptotic minimal gate radius. (C) The S4 segments of the VS domains change translational position z in the exponential region of the G/V relation. Voltages ≤50 mV tend to exclude VS domains from translations that allow conduction. Note that panels B and C show the expectation values 〈r〉 and 〈z〉 in the full-channel model.