FIGURE 4.

Pore openness as a function of SNARE copies per liposome or vesicle curvature. (A) The fraction $f_{P_o\ge 0.90}$ of open pores $\left(P_o\ge 0.90\right)$ , as a function of average v-SNARE copies per SUV, $N_{SNARE}$ . The fraction increases up to $N_{SNARE}\approx 30$ , to reach ∼0.5. (B) Pore openness for flickering pores $\left(P_o<0.90\right)$ , as a function of $N_{SNARE}$ . The red circles are original data points (light blue) smoothed with a moving average filter with span = 5. The dashed line is a linear fit to the smoothed data with slope 0.0094 (95% confidence interval = 0.0051–0.0138, $R^2=0.15$ ). Note that because v-SNAREs are reconstituted with random orientation, only ∼1/2 would face outside and contribute to fusion. (C) There is no clear correlation between the fraction $f_{P_o\ge 0.90}$ of open pores $\left(P_o\ge 0.90\right)$ and total membrane curvature, $C=2/R_{ves}$ . (D) Pore openness for flickering pores ( $P_o<0.90$ ), as a function of membrane curvature. For flickering pores $\left(P_o<0.90\right)$ , $P_o$ decreases with increasing curvature for vesicle curvatures that correspond to $N_{SNARE}^{out}\approx 15$ (indicated by a vertical dashed line) or smaller. Symbols represent original and smoothed data points as in (B). For (A,C), 164 events were analyzed. For (B,D), 128 events were analyzed.