Figure 3. Two types of fusion events in cells overexpressing CSP and its phosphomutants.

A, Cumulative probability of peak amplitudes for all events ≥2 pA. Inset, expanded view of this cumulative probability in the 2 to 4 pA amplitude range. B, Representative traces of kiss-and-run (KR) (left) and full-fusion (right) events. Two durations distinguish KR from full-fusion events. Duration t₁ (green) represents the duration from signal onset to when the signal falls back to the average value above the 50% peak amplitude. Duration t₂ (red) represents the duration from onset to when the signal returns to within 1×RMS noise of the baseline. Black dashed lines, the peak amplitude of the event. Gray solid lines, 50% of peak amplitude. Blue dashed lines, the average value of the data within 50–100% peak amplitude. Gray dashed lines, baseline (horizontal) or the time boundaries (vertical) for duration t₁ or t₂. Blue squares, the end point of duration t₁. C, Peak amplitudes, mean amplitudes, and duration ratios can be obtained from individual KR events. D, Scatter plots of duration ratios (t₁/t₂) vs. peak amplitudes for events in all groups (n = 5583–9198 events). Duration ratios were averaged for events with peak amplitudes in the same bin and plotted versus peak amplitude (Note that we acquired all signals with the peak amplitude ≥1 pA here). Solid lines indicate the linear fits for the events with peak amplitude >3.5 pA. Dashed lines indicate the transition point (3.5 pA of peak amplitude) between the solid lines and the rising phase of the data.