The rate constant k₀ and voltage-dependent charge q for each unique transition in the model shown in Fig. 6 A, where the final transition rate k at any given voltage is computed as $k=k0e−qv/kBT,$ where V is voltage, k_B is Boltzmann’s constant, and T is temperature. The factors x and y are constants reflecting the degree of cooperativity in the model between activation of the DI–III voltage sensors and activation of the DIV voltage sensor or binding of the fast inactivation motif, respectively. The charges associated with α_4o, β_4o, i_o, and r_o were constrained to be identical to those of α₄, β₄, i, and r, respectively. Similarly, the charges associated with γ₄, δ₄, γ_i, and δ_i were constrained to be identical to those of γ and δ. The rate constants for γ₄ and γ_i were constrained based on microscopic reversibility as $γ4=δ4β4xβ3γα4o / β4oδα4xα3$ and $γi=δiryβ3γ4io / roδ4iyα3,$ in that order.

DI/II/III-CN rates only apply to the middle set of horizontal transitions associated with DI–III voltage sensors.