Figure 3. Fusion pore expansion, constriction and closure at different rates.

(A–E) PH-Ω fluorescence (F_PH, normalized to baseline), A532 spot fluorescence (F₅₃₂, normalized to baseline), Pore_v W_H, and sampled images at times indicated with lines showing different Pore_v dynamics: A, rapid opening and slow constriction (same PH-Ω as in Figure 2H-iv); B, delayed expansion; C, rapid constriction and closure; D, Pore_v unchanged; E, Pore_v disappearance due to Ω-profile shrinking.

A and C: the rate of Pore_v W_H changes (Rate) are plotted (A, 26 ms/frame; C, 46 ms/frame); insets, W_H and Rate at larger time scale. Gray circles in A–B refer to non-visible A532-permeable pores with a W_H <60 nm. Fusion was induced by depol_1s at 0.1–2 s before PH-Ω appeared.

(F) Left, number of Pore_v observed at the fusion onset or 0.5–4 s after fusion (delay).

Right, number of Pore_v that subsequently constricted, constricted and closed, remained unchanged, or disappeared. Data from 51 Pore_v (49 cells, XZ/Y_fix image every 26–300 ms).

See also Figures S2 and S4.