Mineral Surface Photoelectrochemistry to Reduce Inorganic Carbon and Form the Prebiotic Soup

How did life begin?

We are investigating mineral surface photoelectrochemistry as a pathway to reduce inorganic carbon and form a prebiotic soup of organic precursors to life. Basic project questions are: What C_xH_yO_zS_aN_b molecular products result from CO and CO₂ photoreduction over semiconductor supports? What important synthesis reactions relevant to prebiotic chemistry, which are otherwise "no go" via thermal pathways, become possible through semiconductor photocatalysis? Relevant semiconductors for early Earth include ZnS, TiO₂, ZnO, and MnS. The list expands for chemistry occurring on interstellar dust, which may have seeded organic molecules into the prebiotic soup.

From the five known mechanisms by which autotrophic organisms fix carbon, a reductive tricarboxylic acid (rTCA) cycle has been proposed as the most plausible metabolic pathway of CO₂ fixation at the time life originated. A nonenzymatic rTCA cycle might have functioned as an autocatalytic network of chemical reactions able to provide and self-sustain the biosynthetic pathways essential for life to originate. For these reasons, we are currently studying the kinetics of some reactions of the reverse Krebs cycle driven by mineral photochemistry, and the thermal competition pathways. We intend to understand if this chemical cycle could have been related to the origin of prebiotic metabolism.

We are grateful for support received from the Harvard Origins of Life Initiative and the NASA Exobiology Program.

Link

The Harvard origins of life initiative

People Involved

• Current Group Members

  • Marcelo Guzman
  • Scot Martin

Publications

1. M. Guzman and S.T. Martin, "Prebiotic metabolism: Production by mineral photoelectrochemistry of a-ketocarboxylic acids in the reductive tricarboxylic acid cycle," submitted March 2009.

2. M.I. Guzman and S.T. Martin, "Oxaloacetate-to-malate conversion by mineral photoelectrochemistry and implications for the viability of the reductive tricarboxylic acid cycle in prebiotic chemistry," International Journal of Astrobiology, 2008, 7, 271-278. PDF file.

3. A. Tarnowski, X. Zhang, C. McNamara, S. T. Martin, and R. Mitchell, "Biodeterioration and Performance of Anti-graffiti Coatings on Sandstone and Marble," Journal of the Canadian Association for Conservation, 2007, 32, 3-16. PDF File.

4. X.V. Zhang, S.P. Ellery, C.M. Friend, H.D. Holland, F.M. Michel, M.A.A. Schoonen, and S.T. Martin, "Photodriven Reduction and Oxidation Reactions on Colloidal Semiconductor Particles: Implications for Prebiotic Synthesis," Journal of Photochemistry and Photobiology A: Chemistry, 2006, 185, 301-311. PDF File.

5. X.V. Zhang and S.T. Martin, "Driving Krebs Cycle in Reverse through Mineral Photochemistry," Journal of the American Chemical Society, 2006, 128, 16032. PDF File. Press Received.

6. Michel, F.M., Schoonen, M.A.A., Zhang, X.V., Martin, S.T., and Parise, J.B., "Hydrothermal Synthesis of Pure a-Phase Manganese (II) Sulfide Without the Use of Organic Reagents," Chemistry of Materials, 2006, 18, 1726-1736. PDF File.

7. Perry, T.D., Klepac-Ceraj, V., Zhang, X.V., McNamara, C.J., Poltz, M.F., Martin, S.T., Berke, N., and Mitchell, R., "Binding of harvested bacterial exopolymers to the surface of calcite," Environmental Science and Technology, 2005, 39, 8770-8775. PDF File.

8. Zhang, X.V., S.T. Martin, C.M. Friend, M.A.A. Schoonen, and H.D. Holland, "Mineral-Assisted Pathways in Prebiotic Synthesis: Photoelectrochemical Reduction of Carbon(+IV) by Manganese Sulfide," Journal of the American Chemical Society, 2004, 126, 11247-11253. PDF File.