Kazutoshi Iwamoto

Spontaneous appearance of chirally asymmetric steady states in a reaction model including Michaelis–Menten type catalytic reactions

Based on a chemical oscillation model which includes both an autocatalytic and a Michaelis–Menten type catalytic reaction, a chiral symmetry breaking reaction model was constructed and its symmetry breaking transition resulting in the dominance of one enantiomer and the disappearance of the other was studied. Symmetry breaking behavior of the system depends not only on the stereoselectivity of the autocatalytic reaction but also on the stereospecificity of the Michaelis–Menten type catalytic reaction, and it was shown that a chiral symmetry breaking transition can take place even though the selectivities of these reactions are not so high. For example, when the Michaelis–Menten type catalytic reaction is perfectly stereospecific, a chirally asymmetric steady state appears even though the enantiomeric excess of the stereoselective autocatalytic reaction is less than 40%. That is, a stereoselective autocatalytic reaction is always needed for any chiral symmetry breaking transition, but its stereoselectivity need not to be high. Until now, many chemical oscillation systems, which always include an autocatalytic process, have been reported already. Accordingly, if the autocatalyst possesses optical isomers and each isomer catalyzes its own production, spontaneous appearance of a chiral symmetry breaking state can be observed in the chemical oscillation system under an appropriate experimental condition, even though the stereoselectivity in the autocatalytic reaction is not so high.

Spontaneous appearance of chirally asymmetric steady states in a reaction model including imperfectly stereoselective, chirally autocatalytic reactions

Based on the famous Brusselator chemical oscillation model, a reaction model including imperfectly stereoselective, chirally autocatalytic reactions was constructed to investigate the conditions for the spontaneous appearance of chirally asymmetric steady states, and it was shown that a symmetry-breaking transition takes place even under an imperfectly stereoselective situation, leading to a chirally asymmetric steady state spontaneously, under nonequilibrium conditions far from equilibrium. For the symmetry-breaking transition, stereoselective, chirally autocatalytic reactions are always needed but it is not necessary that they are highly selective.