Figure 3.

Area exchange during bleb expansion. In each plot, we present ${\varphi }_{\text{t}}^{\text{eq}}$ (black line), ϕ_t in the bleb state (orange line), and ϕ_t + ΔS_b/A (blue line, also proportional to the tension, σ = σ₀ + k_σ(ϕ_t + ΔS_b/A)) as functions of ΔS_b (see Eq. 5). The vertical gap between the black and orange curves (light orange region) is proportional to the tube-flattened area, and the vertical gap between the blue and black curves (light blue region) is proportional to the stretched area (seized from membrane fluctuations). The dependence on parameters is indicated by the black dashed grid line (saturation limit of tubulation), the orange dashed grid line ($\mathit{\Delta }{S}_{\text{b}}^{\text{flat}}$, given in Eq. 14, beyond which the bleb expansion induces tube flattening), the horizontal gray line (marking the total protein surface fraction ϕ), and the orange tick, which marks the critical bleb expansion, $\mathit{\Delta }{S}_{\text{b}}^{\text{∗}}$ (Eq. 13), beyond which ${\varphi }_{\text{t}}\simeq 0$. We vary the protein surface fraction ϕ, such that the equilibrium tubulation is maximal in plot (a) (${\varphi }_{\text{t}}^{\text{eq}}\simeq \varphi$), and saturated in plot (b) $\left({\varphi }_{\text{t}}^{\text{eq}}\simeq \left(\mathit{\epsilon }-{\sigma }_{0}s\right)/k_{\sigma }s\right)$. We set (ε − σ₀s) = 30 and k_σs = 50 as in Fig. 2, a1 and a2. To see this figure in color, go online.