Figure 1.

Automatic identification and analysis of fusion events. (A) The framework of the algorithm, comprising five steps (non-rounded rectangles). (B) An example of a typical fusion in an INS-1 cell labeled by VAMP2-pHluorin (left) and its central intensity profile (right). The rapid increase in the central intensity indicates the opening of a fusion pore; thus, the peak/background ratio (parameter R₁) can be used to detect candidate events. (C) Consecutive image subtraction of (B) and its central intensity profile; only those peak increases that are greater than the background fluctuation by R₂ will be considered candidate events. The montages are 19 × 19 pixels shown at 0.5-s intervals, and the corresponding kymographs (below) are 150 s. (D) The performance of the method for pHluorin-labeled fusion events (n = 1701 events from 6 cells for VAMP2 and n = 531 events from 7 cells for IRAP). R₁ and R₂ were set to 1.3 and 3 in both situations. Error bars are ±SE.