Table I. Summary of symbols Symbol... | Rockefeller University Press

Table I.

Summary of symbols

Symbol	Definition
Q_EFF(V)	Effective equilibrium constant corresponding to movement of the S1–S4 voltage sensors (Fig. 1, C and E)
L	Equilibrium constant representing the subsequent (“late”) concerted opening of the S6 intracellular gate (Fig. 1, C and E)
a	S6 mutations act by multiplying L by this scaling factor
ΔG_CO,WT	Energy required to activate the native (wild-type) channel (Eq. 1)
ΔΔG_a	Additional energy needed to activate a mutant versus native channel (Eq. 1)
ΔV_1/2	Change in voltage required for half-maximal opening of mutant versus native channels
J(Ca²⁺)	Effective equilibrium constant describing the Ca²⁺-mediated transition between active (top row) and inactive (bottom row) conformations in Fig. 1 (C and E); J(Ca²⁺) ≈ P_O‑PEAK/K_eff
K_eff	A constant closely analogous to the effective Ca²⁺ dissociation constant for CDI, which has been experimentally estimated at a value far less than unity (Tadross et al., 2008)
P_O-PEAK	Peak open probability shortly after membrane depolarization (Eq. 2)
P_O-SS	Steady-state open probability after a prolonged depolarization; for cases 1 and 2, P_O-SS = P_O-PEAK · (1 − F_CDI) (Eq. 3); for case 3, P_O-SS = P_O-PEAK · (1 − F_CDI· CDI_max) (Eq. 5)
CDI	CDI, defined as fraction of peak current lost at steady state; for cases 1 and 2, CDI = F_CDI (Eq. 4); for case 3, CDI = F_CDI · CDI_max (Eq. 5)
F_CDI	Fraction of inactivated channels at steady state (Eq. 4)
CDI_max	Fractional change in open probability of the normal mode versus the inactivated mode (Eq. 5)
VDI₅₀, VDI₃₀₀	Experimental measure of VDI after 50 and 300 ms of depolarization (see Fig. 2 A and Materials and methods)
CDI₅₀, CDI₃₀₀	Experimental measure of CDI after 50 and 300 ms of depolarization (see Fig. 2 A and Materials and methods)

Symbol	Definition
Q_EFF(V)	Effective equilibrium constant corresponding to movement of the S1–S4 voltage sensors (Fig. 1, C and E)
L	Equilibrium constant representing the subsequent (“late”) concerted opening of the S6 intracellular gate (Fig. 1, C and E)
a	S6 mutations act by multiplying L by this scaling factor
ΔG_CO,WT	Energy required to activate the native (wild-type) channel (Eq. 1)
ΔΔG_a	Additional energy needed to activate a mutant versus native channel (Eq. 1)
ΔV_1/2	Change in voltage required for half-maximal opening of mutant versus native channels
J(Ca²⁺)	Effective equilibrium constant describing the Ca²⁺-mediated transition between active (top row) and inactive (bottom row) conformations in Fig. 1 (C and E); J(Ca²⁺) ≈ P_O‑PEAK/K_eff
K_eff	A constant closely analogous to the effective Ca²⁺ dissociation constant for CDI, which has been experimentally estimated at a value far less than unity (Tadross et al., 2008)
P_O-PEAK	Peak open probability shortly after membrane depolarization (Eq. 2)
P_O-SS	Steady-state open probability after a prolonged depolarization; for cases 1 and 2, P_O-SS = P_O-PEAK · (1 − F_CDI) (Eq. 3); for case 3, P_O-SS = P_O-PEAK · (1 − F_CDI· CDI_max) (Eq. 5)
CDI	CDI, defined as fraction of peak current lost at steady state; for cases 1 and 2, CDI = F_CDI (Eq. 4); for case 3, CDI = F_CDI · CDI_max (Eq. 5)
F_CDI	Fraction of inactivated channels at steady state (Eq. 4)
CDI_max	Fractional change in open probability of the normal mode versus the inactivated mode (Eq. 5)
VDI₅₀, VDI₃₀₀	Experimental measure of VDI after 50 and 300 ms of depolarization (see Fig. 2 A and Materials and methods)
CDI₅₀, CDI₃₀₀	Experimental measure of CDI after 50 and 300 ms of depolarization (see Fig. 2 A and Materials and methods)