Miller experiments in atomistic computer simulations
Antonino Marco Saittaa,b,1 and Franz Saijac,1
aSorbonne Universités, Université Pierre et Marie Curie Paris 06, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Unité Mixte de Recherche 7590, 75005 Paris, France;
bCentre National de la Recherche Scientifique, Unité Mixte de Recherche 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75005 Paris, France; and
cCNR-Istituto per i Processi Chimico-Fisici, V. le F. Stagno d'Alcontres 37, 98158 Messina, Italy
Edited by Michael L. Klein, Temple University, Philadelphia, PA, and approved August 8, 2014 (received for review February 15, 2014)
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In 1953, Stanley Miller reported on the spontaneous formation of glycine when applying an electric discharge on a mixture of simple molecules, giving birth to modern research on the origins of life. The effect of electric fields on mixtures of simple molecules is presently studied in computer simulations at the quantum level, and Miller results are reproduced for the first time, to our knowledge, in atomistic simulations, as glycine forms spontaneously only in the presence of electric fields. However, this occurs through reaction pathways more complex than believed, identifying formamide as a key compound in prebiotic chemistry. Moreover, electric fields are naturally present at mineral surfaces, suggesting a potentially crucial role in the biogeochemistry of both the primordial and the modern Earth.
The celebrated Miller experiments reported on the spontaneous formation of amino acids from a mixture of simple molecules reacting under an electric discharge, giving birth to the research field of prebiotic chemistry. However, the chemical reactions involved in those experiments have never been studied at the atomic level. Here we report on, to our knowledge, the first ab initio computer simulations of Miller-like experiments in the condensed phase. Our study, based on the recent method of treatment of aqueous systems under electric fields and on metadynamics analysis of chemical reactions, shows that glycine spontaneously forms from mixtures of simple molecules once an electric field is switched on and identifies formic acid and formamide as key intermediate products of the early steps of the Miller reactions, and the crucible of formation of complex biological molecules.
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Author contributions: A.M.S and F.S. designed research; F.S. performed the classical simulations; A.M.S. performed the ab initio calculations and analyzed the results; and A.M.S. and F.S. wrote the manuscript.
The authors declare no conflict of interest.
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