Abstract
We propose a model for chiral polymerisation and investigate its symmetric and asymmetric solutions. The model has a source species which decays into left- and right-handed types of monomer, each of which can polymerise to form homochiral chains; these chains are susceptible to 'poisoning' by the opposite-handed monomer. Homochiral polymers are assumed to influence the proportion of each type of monomer formed from the precursor. We show that for certain parameter values a positive feedback mechanism makes the symmetric steady-state solution unstable. The kinetics of polymer formation are then analysed in the case where the system starts from zero concentrations of monomers and chains. We show that following a long induction time, extremely large concentrations of polymers are formed for a short time, during this time an asymmetry introduced into the system by a random external perturbation may be massively amplified. The system then approaches one of the steady-state solutions described above.
Highlights
Studies of the origins of life raise many associated fundamental questions
We show that following a long induction time, extremely large concentrations of polymers are formed for a short time, during this time an asymmetry introduced into the system by a random external perturbation may be massively amplified
What leads to the synthesis of homochiral polymers, in which all the constituent monomers have the same handedness ? And what is responsible for the evolution of chiral purity, the more or less exclusive dominance of one macromolecular handedness over its mirror image? These are questions of great interest and importance and remain the subject of much discussion
Summary
Studies of the origins of life raise many associated fundamental questions. Among these, one is concerned with the origin and propagation of molecular handedness. For the case of proteins, there is the driving force of the beneficial secondary structures, such as α-helices and β-sheets, that may arise from homochiral polymers. Given these assumptions, that wrong-handed monomers inhibit chain growth, our paper is concerned with whether, starting from a racemic mixture of monomers, it is possible to produce a system of homochiral polymers of a greater or lesser degree of chiral purity. Starting from an achiral substrate, we shall be concerned with whether it is possible to produce a system of homochiral polymers of high chiral purity by analysing some plausible kinetic models
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Schedule a callMore From: Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life
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