Isoleucine as a possible bridge between exogenous delivery and terrestrial enhancement of homochirality

Abstract

We report a highly enantioselective oligomerization of isoleucine stereomers in the salt-induced peptide formation reaction under plausibly prebiotic earth conditions. Up to 6.5-fold superiority in reactivity of L-isoleucine was observed, compared to its D-enantiomer, after 14 evaporation cycles in the presence of Cu(2+) and NaCl. Since isoleucine is among the proteinogenic amino acids that were found enantioenriched in meteorites, this present work may further correlate the extraterrestrial delivery and endogenous production of biological homochirality by virtue of a protein constituent rather than the rarely occurring α-methylated amino acids.