Spontaneous chiral symmetry breaking in early molecular networks

Abstract

BackgroundAn important facet of early biological evolution is the selection of chiral enantiomers for molecules such as amino acids and sugars. The origin of this symmetry breaking is a long-standing question in molecular evolution. Previous models addressing this question include particular kinetic properties such as autocatalysis or negative cross catalysis.ResultsWe propose here a more general kinetic formalism for early enantioselection, based on our previously described Graded Autocatalysis Replication Domain (GARD) model for prebiotic evolution in molecular assemblies. This model is adapted here to the case of chiral molecules by applying symmetry constraints to mutual molecular recognition within the assembly. The ensuing dynamics shows spontaneous chiral symmetry breaking, with transitions towards stationary compositional states (composomes) enriched with one of the two enantiomers for some of the constituent molecule types. Furthermore, one or the other of the two antipodal compositional states of the assembly also shows time-dependent selection.ConclusionIt follows that chiral selection may be an emergent consequence of early catalytic molecular networks rather than a prerequisite for the initiation of primeval life processes. Elaborations of this model could help explain the prevalent chiral homogeneity in present-day living cells.ReviewersThis article was reviewed by Boris Rubinstein (nominated by Arcady Mushegian), Arcady Mushegian, Meir Lahav (nominated by Yitzhak Pilpel) and Sergei Maslov.

Excess Mutual Catalysis Is Required for Effective Evolvability

“…While for the smaller N max value, the percentage of beneficial outcomes seems to be even higher than for the nominal N max = N G , a larger N max value appears to have a disruptive effect because the system is nearing the equilibrium steady state [23]. This is especially seen for the compotype count and the evolvability score.…”

“…The GARD model embodies the inheritance of compositional information in the realm of a lipid world scenario for early evolution [20,21,23,27,48,49,51,[55][56][57]. The GARD has recently been pursued in several additional publications [20,39,68,70] and has been chosen as an archetypal metabolism-first realization [68].…”

Possible Roles of Amphiphilic Molecules in the Origin of Biological Homochirality

“…One reason for this is that it has been thought that the first biological entities were biopolymers, such as proteins and RNA, rather than lipids; thus, the discussion of homochirality has been mainly limited to biopolymers. The question was examined relatively recently [13,103] (p. 303). The relation between a supramolecular assembly and chirality is complicated compared to biopolymers, and it is necessary to clarify the connection between the features of an amphiphilic molecule and homochirality.…”

The Chain of Chirality Transfer as Determinant of Brain Functional Laterality. Breaking the Chirality Silence: Search for New Generation of Biomarkers; Relevance to Neurodegenerative Diseases, Cognitive Psychology, and Nutrition Science

“…The diversity of stereospecific (chiral) phenomena was observed in molecular structures including chirality recognition/sensing [95,96], chirality transfer [97], chirality/helicity induction [98][99][100][101], chirality amplification [102][103][104], chirality breaking [61,105], chirality conflict [106,107], helicity inversion [108][109][110], and chiral phase transitions XVII [111][112][113][114]116]. Progress in the studies of molecular chirality transformation is helpful in resolving three questions.…”