Formation of polyamino acids in the prebiotic conditions : production mechanisms and structures.

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It is important for research of the origins of life to elucidate polyamino acid formation in the prebiotic conditions. Only a limited set of amino acids has been reported to polymerize thermally.In this study, oligopeptides formed in the heating experiments of aqueous aspargine and ureaamino acids mixtures were characterized individually using a liquid chromatograph-mass spectrometer. Cooligomerization of aspargine and other amino acids were well characterized as the amide exchange mechanism proposed in our previous paper. We also demonstrate a novel thermal polymerization in molten urea of alkylamino acids (i.e.glycine, alanine, α-alanine, β-aminobutyric acid, valine, norvaline, leucine, and norleucine) which had been thought to be incapable of undergoing thermal polymerization. Also, aspartic acid was found to polymerize in molten urea at a lower temperature than that at which aspartic acid alone had previously been thermally polymerized. The polymerization reaction occurred by taking advantage of molten urea's high polarity as well as its dehydrating ability. Under the presumed prebiotic conditions employed here, many types of amino acids were thus revealed to undergo thermal polymerization.Some novel information of polyamino acid formation in the prebiotic conditions were obtained through this study. In addition, we found some directivity in future research for the study of origins of life.