Movie 3. Probability [Low affinity] = 1 (fast). The simulation of Movie 2 is repeated, but now for 200,000 steps with only every 200th frame being displayed. Each blue square in the bottom compartment indicates that 100 ions have crossed. During this simulation, 400 K and 399 Na ions have permeated, making the K/Na flux ratio close to 1. If this simulation is repeated many times, the mean ratio is statistically indistinguishable from 1: the low-affinity state has no ion selectivity.     (Movie 4)    (Back)