Plural Origins of the Molecular Homochirality in Our Biota

Abstract

Abstract We describe results of computer simulation calculations of mixed and homochiral oligoribotides showing that it is possible to bind ʟ( D)-monomers at the term in al positions of chains built from D (L )-ribotides, but insertion at internal positions produces a large in stability of the chains. Coupled with aproposed new mechanism for the growth of these lin ear polymers in prebiotic conditions, our results imply that enantiomericcross-inhibition could have been bypassed to make all-D(ʟ) oligoribotidesdominant. We also show that racemic amino acids can form stable peptide β-strands, which rules out a similar origin for modern L -amino acids. Alternative schemes are proposed to account for the homochiralities of the amino acids and of other bio molecules.