The Role of Submarine Hydrothermal Systems in the Synthesis of Amino Acids
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There is little consensus regarding the plausibility of organic synthesis in submarine hydrothermal systems (SHSs) and its possible relevance to the origin of life. The primary reason for the persistence of this debate is that most experimental high temperature and high-pressure organic synthesis studies have neglected important geochemical constraints with respect to source material composition. We report here the results of experiments exploring the potential for amino acid synthesis at high temperature from synthetic seawater solutions of varying composition. The synthesis of amino acids was examined as a function of temperature, heating time, starting material composition and concentration. Using very favorable reactant conditions (high concentrations of reactive, reduced species), small amounts of a limited set of amino acids are generated at moderate temperature conditions (∼125–175°C) over short heating times of a few days, but even these products are significantly decomposed after exposure times of approximately 1 week. The high concentration dependence observed for these synthetic reactions are demonstrated by the fact that a 10-fold drop in concentration results in orders of magnitude lower yields of amino acids. There may be other synthetic mechanisms not studied herein that merit investigation, but the results are likely to be similar. We conclude that although amino acids can be generated from simple likely environmentally available precursors under SHS conditions, the equilibrium at high temperatures characteristic of SHSs favors net amino acid degradation rather than synthesis, and that synthesis at lower temperatures may be more favorable.
KeywordsSubmarine hydrothermal systems Amino acids Prebiotic chemistry Origin of life Abiotic synthesis
This work was supported by the NASA Specialized Center of Research and Training (NSCORT) in Exobiology, a grant from the UCSD Academic Senate Committee on Research, and in part by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by Oak Ridge Associated Universities through a contract with NASA. The authors would like to thank Dr. John H. Chalmers for laboratory assistance, and Dr. Evan A. Solomon and Prof. Joris M. Gieskes for helpful discussions. Special thanks are offered to Prof. Robert White and anonymous reviewers whose comments helped greatly improve this manuscript.
- Borsook H, Huffman HM (1933) The free energies of formation of aqueous d-alanine, l-aspartic acid, and d-glutamic acid. J Biol Chem 99:663–676Google Scholar
- Chang S (1993) Prebiotic synthesis in planetary environments. In: Greenberg JM, Mendoza-Gomez CX, Pirronello V (eds) The chemistry of life's origins. NATO ASI series C. vol. 416. Kluwer, Dordrecht, pp 259–299Google Scholar
- Charlou JL, Donval JP, Douville E, Jean-Baptiste P, Radford-Knoery J, Fouquet Y, Dapoigny A, Stievenard M (2000) Compared geochemical signatures and the evolution of Menez Gwen (37°50′N) and Lucky Strike (37°17′N) hydrothermal fluids, south of the Azores Triple Junction on the Mid-Atlantic Ridge. Chem Geol 171:49–75CrossRefGoogle Scholar
- Corliss JB, Baross JA, Hoffman SE (1981) An hypothesis concerning the relationship between submarine hot springs and the origin of life on Earth. Oceanologica Acta 4(Suppl.):59–69Google Scholar
- Holland HD (1984) The chemical evolution of the atmosphere and oceans. Princeton University Press, New JerseyGoogle Scholar
- Islam MN, Kaneko T, Kobayashi K (2001) Determination of amino acids formed in a supercritical water flow reactor simulating submarine hydrothermal systems. Anal Sci 17:1631–1634Google Scholar
- Schwartz AW (1981) Chemical evolution - the genesis of the first organic compounds. In: Duursma EK, Dawson R (eds) Marine organic chemistry. Elsevier Oceanography Series, Amsterdam, pp 7–30Google Scholar
- Walker JF (1964) Formaldehyde, 3rd edn. ACS Monograph Series 159, Reinhold Publishing Corporation, New YorkGoogle Scholar