Pathways for the asymmetric amplification of protein amino acids in the Murchison meteorite

ABSTRACT The amplification of L-enantiomers of amino acids from racemates was likely a precondition for the origin of life on Earth. Engel and Nagy 1 first reported that seven protein amino acids in the Murchison meteorite exhibited a significant L-enantiomer excess, leading to speculation that meteorite bombardment during the earliest stages of Earth history provided these essential building blocks for the development of life. Stable isotope signat ures of amino acids extracted from the Murchison meteorite confirmed the extraterrestrial origin and stereochemistry of these compounds 2,3 . However, until recently, plausible explanations for the observed magnitude of the L-enantiomer excess in Murchison have been lacking. Alternative methods for the asymmetric amplification of L-amino acids have recently been reported e.g.4,5 that are consistent with that observed in the Murchison meteorite. A model is presented for the synthesis and subsequent alteration of amino acids on the parent body of the Murchison meteorite that is consistent with the stereochemistry presently observed. Keywords: amino acids, stereochemistry, Murchison Meteorite, stable isotopes