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Prebiotic formation of polyamino acids in molten urea

Published online by Cambridge University Press:  04 October 2005

H. Mita
Affiliation:
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan e-mail: mita@staff.chem.tsukuba.ac.jp
S. Nomoto
Affiliation:
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan e-mail: mita@staff.chem.tsukuba.ac.jp
M. Terasaki
Affiliation:
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan e-mail: mita@staff.chem.tsukuba.ac.jp Institute for Environmental Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
A. Shimoyama
Affiliation:
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan e-mail: mita@staff.chem.tsukuba.ac.jp Institute for Environmental Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
Y. Yamamoto
Affiliation:
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan e-mail: mita@staff.chem.tsukuba.ac.jp

Abstract

It is important for research into the origins of life to elucidate polyamino acid formation under prebiotic conditions. Only a limited set of amino acids has been reported to polymerize thermally. In this paper we demonstrate a novel thermal polymerization mechanism in a molten urea of alkylamino acids (i.e. glycine, alanine, β-alanine, α-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. Individual oligomers produced in heating experiments on urea–amino acid mixtures were analysed using a liquid chromatograph mass spectrometer. Major products in the reaction mixture were three different types of polyamino acid derivatives: N-carbamoylpolyamino acids, polyamino acids containing a hydantoin ring at the N-terminal position and unidentified derivatives with molecular weights that were greater by 78 than those of the corresponding peptide forms. The polymerization reaction occurred by taking advantage of the high polarity of molten urea 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.

Type
Research Article
Copyright
2005 Cambridge University Press

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