Figure 3.

Density profiles as a function of the membrane area a at different times, $\overline{t}$ = [1, 50, 100, 500]dt, for (a) an Ω-shape, (b) a dome shape, (c) a tube, and (d)–(f) pearling structures with different number of pearls. In all simulations, the initial density is given by $\sigma \left(s,\overline{t}=0\right)$ = c(1 − tanh(5(a(s) − a₀))), where c and a₀ are such that σ(a(s = 0), $\overline{t}$ = 0) = 0.5 and m_tot = 0.24. $\sigma \left(s,\overline{t}=0\right)$ represents a nearly uniform protein distribution located at the top of the budding structure. As time proceeds, the initial protein density spreads over the membrane area, where the profiles are qualitatively different. In the case of the Ω- (a) and the pearling shapes (d–f), the protein density has a staircase-like profile along each of the pearls, indicating that the narrow necks prevent the profile from having a smoother transition. The overall effect of the membrane necks on the diffusion on buds and pearls is to slow down the exit of proteins from the budded structure. The corresponding shape is shown in the inset of each panel. To see this figure in color, go online.