Fig. 1

a The energy diagrams above the polymers show the heights of the kinetic barriers for bond formation/dissociation in various regions. Dark- vertical bars are hydrogen bonds with high kinetic barrier, while lighter bars denote bonds with lower kinetic barriers. The balls-and-sticks diagram of polymer growth illustrates the fact that asymmetric cooperativity enables faster strand growth by lowering kinetic barrier for bond formation to the right. Asymmetric kinetic influence of a hydrogen bond on adjacent monomers (raising the barrier of the left bond and lowering it for the right) optimizes strand elongation as well as increases the duration of monomer bonding to the template strand to increase the probability of covalent bond formation. b With symmetric kinetic influence, hydrogen bonds that are away from the growth front (second bond from left) have lower kinetic barriers. Thus, monomers are drawn away from growth front, resulting in lower growth rate. This makes symmetric replicators evolutionarily inferior (From Ref [26], with permission)