Souping up the prebiotic soup

Novel chiral amplification with links to origin of life.

What is the origin of life? Whilst not yet able to give a definitive answer to this ever-present question, David Kelly and his colleagues at Cardiff University and the University of Liverpool, UK, claim that by understanding how only the D-sugars and L-amino acids (and not a mixture of their enantiomers) came to be present in nature is a key stepping stone along the path to understanding how life itself came to be.

Kelly and his colleagues were interested in a known reaction which uses a peptide to catalyse an enantioselective epoxidation. The peptide is made from the amino acid leucine and it appears that the enantioselection depends only on the configuration of the ends of the peptide chain. Intrigued by this observation they examined the change in product enantiomeric excess as the ratio of leucine monomer enantiomers was varied.

Their results show that a modest monomer enantiomeric excess gives oligomers with highly enantioselective catalytic activity, and agree with their theoretically predicted enantiomeric excesses. This system is the first metal-free chiral amplification system.

Although they caution that links with the origin of life are entirely speculative, Kelly imagines that ’on the prebiotic earth, crystalline conglomerates might slowly dissolve and polymerise to give enantiomerically enriched peptides in the same way that we have achieved in the laboratory. These in turn will catalyse enantioselective reactions.

’How this evolves into life is a much bigger question, but we have at least shown a plausible way for single enantiomers to be made by a chiral amplification process, from simple precursors believed to be present in the prebiotic soup.’

Caroline Evans