Segregated vs. mixed models at full β subunit site occupancy. (A) Schematic of how different β subunit isoforms would be distributed in a channel population in a segregated model. (B) Stoichiometric possibilities in accordance with a random mixing model. (C) Predictions for how slow tail amplitude (A_ST) will vary as mole fractions of β2 and β3a are varied and does not differ between random mixed and segregated models, assuming that likelihood of inactivation by either β2 or β3a N termini is identical. (D) Illustration of how differences in β2 and β3a inactivation likelihood will impact A_ST as a function of nominal β2/β3 mole fraction, where k_β3a/k_β2 reflects the ratio of β2 and β3a likelihoods, e.g., as suggested by the ratio of differences in β3a vs β2 inactivation onset.