Table 2.

M-model 1 rate constants for transitions within hERG gating for a-isoform and b-isoform.

Transition	Parameter name		Rates		ratio b/a
			b-Isoform	a-Isoform
C3 → C2	ae	α	4.71 E-2	3.39 E-2	1.39
		β	9.36 E-3	1.04 E-2	0.90
C2 → C3	be	α	7.43 E-2	4.82 E-2	1.54
		β	−5.05 E-2	−6.91 E-2	0.73
C2 → C1	ain	α	5.01 E-2	2.20 E-2	2.28
C1 → C2	bin	α	2.95 E-2	1.36 E-2	2.17
I → O	ai	α	2.80 E-2	6.63 E-3	4.23
		β	−3.06 E-2	−3.89 E-2	0.79
O → I	bi	α	7.41 E-2	7.41 E-2	1.00
		β	1.88 E-2	2.80 E-2	0.67
C1 → O	aa	α	1.71 E-2	4.94 E-3	3.46
		β	3.05 E-2	4.31 E-2	0.71
O → C1	bb	α	1.61 E-3	2.06 E-4	7.83
		β	−3.44 E-2	−3.76 E-2	0.91

α (1/ms) indicates voltage independent rate, and β (1/mV) indicates voltage dependent rate as follows: k = α^*exp(β^*V) The transitions between O and I states are also dependent on extracellular potassium concentration [K⁺]⁰. That dependence is accounted for in the model by modifying the transition rate for inactivation (O → I, bi) as: k_bi([K⁺]⁰) = k'_bi(5.4mM/[K⁺]⁰)^0.4. Bold values indicate moderate change of the corresponding transitions calculated as a ratio. Transitions that are strongly affected are shown in bold red. Transitions that are affected the most are shown as underlined red bold values. For details of the optimizations, original model parameters and optimization from CHO data see Tables S1–S4.