Figure 3.

Quantitative docking analysis. (a) Accumulated docking counts as a function of time. Ca²⁺ was added half-way through the series. (b) Schematic illustrating the ROI approach for counting diffusing v-vesicles. The effective dimensions of the applied ROIs are indicated. (c) Trace of diffusing v-vesicles obtained by ROI integration throughout a fusion movie in a region of the surface having no t-vesicles. Diffusing vesicles were counted using a threshold (dashed line). (d) Accumulated count of diffusing vesicles constructed from 676 ROIs. The data were fitted with a straight line to extract the average v-vesicle count. (e) Joint probability, P_J (normalized to 1 to ease comparison), as a function of the intrinsic docking probability, p_d, calculated from the data in panel a for the cases without and with Ca²⁺.