Figure 1:

Description of the computational model. (A) Bottom and (B) side views of shell subunits. Each subunit contains ‘Attractors’ (cyan spheres) on its perimeter, and a ‘Top’ (ochre sphere, ‘TH’ ) and a ‘Bottom’ (white sphere, ‘BH’ ) in the center above and below the subunit plane. Interactions between Attractors drive subunit assembly, while Top-Top and Bottom-Bottom repulsions control the subunit-subunit angle and spontaneous curvature radius of the shell R₀. (C) Scaffolds are bead-spring polymers with three domains: scaffold-cargo binding domain (yellow) beads have attractive interactions with cargo particles, middle domain (green) beads have no attractive interactions with cargo or shell subunits, and scaffold-subunit binding domain (dark blue) beads have attractive interactions with subunit Bottom pseudoatoms ‘BH’. The contour length of the scaffold with N_s beads is denoted as L_s, while the lengths of the domains are L_sc, L_sm, and L_sh, respectively. Excluder atoms (orange pseudoatoms in the plane of the ‘Top’) experience excluded volume interactions with the cargo and scaffold beads. (D) Example of a complete shell with spontaneous curvature radius R₀ = 22, with encapsulated cargo and scaffold molecules with L_s = 64 (L_sc = 7, L_sm = 50, L_sh = 7). All lengths in this article are given in units of r_*, the cargo diameter (the rubisco diameter in carboxysome is ≈13 nm), and energies are in units of the thermal energy k_BT.