The random mixing model better describes trypsin digestion time course than the segregated model. (A) Normalized digestion time course for the indicated (right) nominal injection ratios. Lines are best fits of Eq. 15 (random mixing), with all curves fit simultaneously and only sf was a free parameter (red), while parameters in black were constrained to the indicated values. (B) Simultaneous fit of the segregated model. (C) Sum of squares (SSQ) for comparisons of curves to each individual time course, and also all values together, with the random mixing yielding a fit about 2.5-fold better with the same number of free parameters. Red: random mixing; Gray: segregated. The fit parameter, n, refers to the average number of inactivation domains per BK channel in the channel population.