Figure 5. Doc2b concentration dependence of membrane stalk formation.

(a) Cumulative distributions, (b) stalk formation probabilities at 0 nM (1 event during 661 trials), 5.9 nM (4 events out of 521 trials), 29 nM (7 events out of 777 trials), 0.15 μM (24 events out of 694 trials) and 0.74 μM (117 events out of 458 trials) Doc2b. Error bars indicate the statistical error in the number of counts. (c) Average±s.e.m. of rupture forces at the same Doc2b concentrations observed during bead separation in the presence of 20% PS and 250 μM Ca²⁺. Numbers of above-threshold events are indicated in the graph. A strong increase in the probability of stalk formation was observed as a function of Doc2b concentration.