Abstract
Spontaneous mirror symmetry breaking (SMSB), a phenomenon leading to non-equilibrium stationary states (NESS) that exhibits biases away from the racemic composition is discussed here in the framework of dissipative reaction networks. Such networks may lead to a metastable racemic non-equilibrium stationary state that transforms into one of two degenerate but stable enantiomeric NESSs. In such a bifurcation scenario, the type of the reaction network, as well the boundary conditions, are similar to those characterizing the currently accepted stages of emergence of replicators and autocatalytic systems. Simple asymmetric inductions by physical chiral forces during previous stages of chemical evolution, for example in astrophysical scenarios, must involve unavoidable racemization processes during the time scales associated with the different stages of chemical evolution. However, residual enantiomeric excesses of such asymmetric inductions suffice to drive the SMSB stochastic distribution of chiral signs into a deterministic distribution. According to these features, we propose that a basic model of the chiral machinery of proto-life would emerge during the formation of proto-cell systems by the convergence of the former enantioselective scenarios.
Highlights
The origin of biological homochirality (BH) [1,2,3,4] is often described as a scientific mystery [5] and the lack of a scientific explanation of the BH phenomenon is often used as proof against the theory of evolution [6]
This means that BH belongs to the same physico-chemical scenarios as those of open chemical networks proposed for the description of minimal self-reproducing proto-cells, primordial biochemical cycles, and the chemical thermodynamics of the reaction networks that maintain the phenomenon of life [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]
Hypothesis on the Emergence of BH. The former sections correspond to an attempt to describe selected concepts from different scientific fields, which are essential for the understanding of the emergence of chirality in chemical evolution and for the description of the basic principles necessary for the understanding of BH
Summary
The origin of biological homochirality (BH) [1,2,3,4] is often described as a scientific mystery [5] and the lack of a scientific explanation of the BH phenomenon is often used as proof against the theory of evolution [6]. In spite of the current mainstream ideas that dominate the possible explanations of BH, there are currently well-established theoretical and experimental chemical reports supporting chemical abiotic scenarios, which show a resilience to racemization and a preference for homochiral reaction outcomes with respect to the racemic ones, i.e. these are the very trends defining BH. We discuss these points with the aim to close the gap in the understanding of SMSB and of its place within the differentiated and hierarchical stages of chemical evolution.
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