  Biological systems are homochiral, raising the question of how a racemic
mixture of prebiotically synthesized biomolecules could attain a homochiral
state at the network level. Based on our recent results, we aim to address a
related question of how chiral information might have flowed in a prebiotic
network. Utilizing the crystallization properties of the central RNA precursor
known as ribose-aminooxazoline (RAO), we showed that its homochiral crystals
can be obtained from its fully racemic solution on a magnetic mineral surface,
due to the chiral-induced spin selectivity (CISS) effect. Moreover, we
uncovered a mechanism facilitated by the CISS effect through which chiral
molecules, like RAO, can uniformly magnetize such surfaces in a variety of
planetary environments in a persistent manner. All this is very tantalizing,
because recent experiments with tRNA analogs demonstrate high stereoselectivity
in the attachment of L-amino acids to D-ribonucleotides, enabling the transfer
of homochirality from RNA to peptides. Therefore the biological homochirality
problem may be reduced to ensuring that a single common RNA precursor (e.g.
RAO) can be made homochiral. The emergence of homochirality at RAO then allows
for the chiral information to propagate through RNA, then to peptides, and
ultimately, through enantioselective catalysis, to metabolites. This
directionality of the chiral information flow parallels that of the central
dogma of molecular biology--the unidirectional transfer of genetic information
from nucleic acids to proteins.
