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The origin of biological homochirality along with the origin of life

Fig 2

Chirality-deviation may result from the template-directed synthesis.

Color legends: Red for D-type and blue for L-type (applicable in all figures of the paper). Enantiomeric excess (‘ee’) equals to (D-L)/(D+L), where D and L represent corresponding enantiomers summed up over all the nucleotide precursors, nucleotides and nucleotide residues in RNA within the system. PTL = 0.01. (a) 50 molecules of D-RNA, 6 nt in length, are inoculated at 1×106 step. PRL = 0 (i.e., de novo appearance of RNA is impossible). Solid line: FCST = 0 (complete chiral-selection); dashed line: FCST = 0.5 (partial chiral-selection); Dash-dotted line: FCST = 1 (no chiral-selection). See S2 Fig for the cases corresponding to more FCST values. The dotted line represents the case in which neither chiral-selection nor cross-inhibition termination exists. (b) RNAs appear de novo. PRL = 1×10−6, FCST = 0.5, FCSS = 0. This is a case in which L-RNA prevails–which is in practice ‘by chance’ (e.g., if using a different random seed in the Monte-Carlo simulation, D-RNA might prevail). The evolution regarding RNA’s chain-length distribution is displayed below, respectively of the two chirality types.

Fig 2