In a new paper published in PNAS, scientists at the Université Pierre et Marie Curie, Sorbonne, Paris, France revisited the famous Miller-Urey experiment, from which the “primordial soup” hypothesis for the origins of life on Earth was born . This new research investigates the role of the electric field in the reaction at a quantum level and, for the first time, reproduces the results of the Miller-Urey experiment in silico.
In the Miller-Urey experiment, first performed in 1952 and published in 1953, Stanley Miller attempted to simulate the conditions of early Earth by combining basic gases and liquids . He then exposed this mixture to an electric spark to mimic lightning. The result was a brown “soup” which contained amino acids, one of the critical building blocks of life.
The current research, led by Antonino Marco Saitta (of the Extreme Physics and Chemistry Community), recreates the conditions of the Miller-Urey experiment using sophisticated computer modeling techniques. Building on previous work on the effects of electric fields on water, Saitta and colleague Franz Saija applied quantum-based ab initio calculation methods to the primordial soup scenario.
In their virtual experiment, Saitta and Saija created a mixture of simple molecules, such as water, ammonia, methane, carbon monoxide, molecular nitrogen, and molecular hydrogen. After this mixture was exposed to an electric field, the reaction simulation produced glycine, an amino acid, thus faithfully reproducing the Miller-Urey experiment. However, the team’s work also provides insight into the precise mechanism of the reaction, pointing to formamide as a major reaction intermediate. This is particularly important since formamide is also important for production of other biologically important compounds such as nucleic acids.
"As a physicist, I dared to undertake this challenging and interdisciplinary work thanks to the familiarity provided, in my institution, by the close interactions with chemists and geoscientists," said Saitta. "I think that the strategy of bringing together scientists from different domains, as the DCO consortium does, is a winning one. In particular, I am glad that this work might help establish more firmly the great reach of modern, state-of-the-art ab initio calculations within the “origins of life” and the geochemistry communities."
These data also provide insight into origins of life work focused on water-rock interactions. The electric field simulated in the current study is an order of magnitude weaker than natural electric fields occurring, at short atomic distances, on mineral surfaces, suggesting a similar reaction mechanism could take place in certain natural environments.
Image: Artist's impression of the effect of lightning or a strong electric field on simple molecules (left: water, ammonia, carbon monoxide), producing first formamide (center) and then the simplest amino acid, glycine (right). A. Marco Saitta (IMPMC/UPMC) and Franz Saija (BIBF/CNR)