The self-replication reaction of hexamers is modelled as a single step: Hi+Tx+Ty→Hi+Hj (i, x, y, and j indices represent the number of A building blocks), where Hi is the hexamer exposed at the end of fiber Ff and Tx and Ty are two trimers bound to it. Hj is the new hexamer (j=x+y). This reaction does not assume a particular mechanism. Its rate was assumed to scale with the binding energy between the newly formed hexamer and that exposed at the fiber end. Similar to how the precursor binding energies were computed, the binding energy between these two hexamers ΣEij was determined based on the sum of the energies associated with the pairing of the constituent building blocks A and B (E AA , E BB and E AB , which can be different from those in Equation ( )). The rate constant is then determined from: