Thermodynamic Potential for the Abiotic Synthesis of Adenine, Cytosine, Guanine, Thymine, Uracil, Ribose, and Deoxyribose in Hydrothermal Systems |
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Authors: | Douglas E LaRowe Pierre Regnier |
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Institution: | (1) Department of Earth Sciences—Geochemistry, Faculty of Geosciences, Utrecht University, P.O. Box 80.021, TA 3508 Utrecht, Netherlands |
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Abstract: | The thermodynamic potential for the abiotic synthesis of the five common nucleobases (adenine, cytosine, guanine, thymine,
and uracil) and two monosaccharides (ribose and deoxyribose) from formaldehyde and hydrogen cyanide has been quantified under
temperature, pressure, and bulk composition conditions that are representative of hydrothermal systems. The activities of
the precursor molecules (formaldehyde and hydrogen cyanide) required to evaluate the thermodynamics of biomolecule synthesis
were computed using the concentrations of aqueous N2, CO, CO2 and H2 reported in the modern Rainbow hydrothermal system. The concentrations of precursor molecules that can be synthesized are
strongly dependent on temperature with larger concentrations prevailing at lower temperatures. Similarly, the thermodynamic
drive to synthesize nucleobases, ribose and deoxyribose varies considerably as a function of temperature: all of the biomolecules
considered in this study are thermodynamically favored to be synthesized throughout the temperature range from 0°C to between
150°C and 250°C, depending on the biomolecule. Furthermore, activity diagrams have been generated to illustrate that activities
in the range of 10−2– 10−6 for nucleobases, ribose and deoxyribose can be in equilibrium with a range of precursor molecule activities at 150°C and
500 bars. The results presented here support the notion that hydrothermal systems could have played a fundamental role in
the origin of life, and can be used to plan and constrain experimental investigation of the abiotic synthesis of nucleic-acid
related biomolecules. |
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Keywords: | Nucleobases Ribose Deoxyribose Hydrothermal systems Thermodynamics |
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