FIGURE 5.
Rules for the formation of intermediates. Note that growth and dissolving compete, so that any intermediate eventually either becomes a complete, stable hexagon or dissolves back into monomers. (a) Two monomers have a probability P1 of joining to begin a new intermediate, which is not yet stably misfolded. Black represents a region blocked by some of their residues. (b) This can grow by addition of monomers to either “end.” After attaching, the monomer sandwiched between the other two has two neighbors and is not allowed to break off, whereas the ones with only one neighbor can. (c) A monomer with only one neighboring monomer has a probability P3 of breaking off in a given step. This competes with the growth process. (d) Continuing addition of monomers can result in a finished hexameric intermediate where every monomer has two neighbors and is safe from breaking off.