Quantifying the Extent of Amide and Peptide Bond Synthesis Across Conditions Relevant to Geologic and Planetary Environments

1,2,3Kirtland J.Robinson,2Christiana Bockisch,2Ian R.Gould,4Yiju Liao,4Ziming Yang,5Christopher R.Glein,2Garrett D.Shaver,2,3Hilairy E.Hartnett,3Lynda B.Williams,2,3Everett L.Shock
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.01.038]
1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543
2School of Molecular Sciences, Arizona State University, Tempe, Arizona, 85287
3School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287
4Department of Chemistry, Oakland University, Rochester, Michigan, 48309
5Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, 78228
Copyright Elsevier

Amide bonds are fundamental products in biochemistry, forming peptides critical to protein formation, but amide bonds are also detected in sterile environments and abiotic synthesis experiments. The abiotic formation of amide bonds may represent a prerequisite to the origin of life. Here we report thermodynamic models that predict optimal conditions for amide bond synthesis across geologically relevant ranges of temperature, pressure, and pH. We modeled acetamide formation from acetic acid and ammonia as a simple analog to peptide bond formation, and tested this model with hydrothermal experiments examining analogous reactions of amides including benzanilide and related structures. We also expanded predictions for optimizing diglycine formation, revealing that in addition to synthesis becoming more favorable at near-ambient pressures (Psat) with increasing temperatures, the strongest thermodynamic drive exists at extremely high pressures (> 15,000 bar) and decreasing temperatures. Beyond implications for life’s origins, the reactants and products involved in simple amide formation reactions can potentially be used as geochemical tracers for planetary exploration of environments that may be habitable.


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