Figure 2

Effects of polymerization length on constriction and fission efficacy and efficiency. (a) Radius of maximum deformation sites, namely the neck radius \(R_n\), at equilibrium (red line with triangles) and at maximum elastic energy (green line with squares), the latter preceding fission for \(H\ge 15\, \text{nm}\), is depicted for increasing values of the coat height H. Critical radius at the coat center, \(R_c\), is shown (blue line with circles), too. The initial radius \(R_\text{in}=\sqrt{k_b/(2\gamma )}\) of the lipid tubule is displayed as a reference (orange line) and the range of theoretically and experimentally predicted critical neck and central radii is reported (light blue stripe)^17,36,41,72. The value \(H=20\,\text{nm}\) divides the abscissa in two different logarithmic scales so as to facilitate perception of all data. (b) Snapshots of tubule portions for different dynamin lengths (\(H=20\,\mathrm {nm}\) above and \(H=70\,\mathrm {nm}\) below) along the evolution. Specifically, from the first to the third columns, the system is depicted in its undeformed, critical, and severed states, respectively. Equilibrium neck radius (red triangle), critical neck radius (green square), and critical central radius (blue circle) are evidenced, too. (c) Maximum elastic energy content of the critical (when preceding fission) or equilibrium (when no fission occurs) configuration with respect to the initial, unperturbed one. The energy of the tubule (red circles) is shown for increasing dynamin heights together with the energy contributions from the central tubular region (orange square) and the outer flanks (blue triangle). This subdivision of the system is illustrated in the critical snapshot at the bottom of the graph (refer to the colored version of the article for better visibility). Experimentally estimated values for the minimal work expenditure of the optimal dynamin machinery¹⁸ is shown for reference (light red stripe). The value \(H=20\,\mathrm {nm}\) divides the abscissa in two different logarithmic scales so as to facilitate perception of all data, whereas the ordinate follows a unique logarithmic scale.