PREBIOTIC SOURCES OF BIOMOLECULAR HANDEDNESS

Fischer demonstrated (1890-1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids, and that in the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality followed without the intervention of the chiral natural force conjectured by Pasteur (1860), except prebiotically. Polarized solar radiation and other classical chiral forces were proposed as agencies generating a prebiotic enantiomeric excess, but the forces then known were found to be evenhanded on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electromagnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomer pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.