Glass flask catalysed famous Miller-Urey origin-of-life experiment

By Jason Arunn Murugesu

Harold Clayton Urey

Harold Urey (1893-1981) was a pioneering chemist

US DEPARTMENT OF ENERGY/SCIENCE PHOTO LIBRARY

A famous origin-of-life experiment from the 1950s may have more accurately mimicked nature than we initially thought.

The influential Miller-Urey experiment showed that with just water, ammonia, hydrogen and methane – and electric sparks to mimic lightning – you could form several of the protein precursors necessary for life on Earth. Stanley Miller and Harold Urey’s aim was to recreate the chemical conditions of early Earth.

But what the researchers had never explicitly considered was whether the nature of the container used in the experiment had any effect on the outcome.

“We don’t know why no one looked at this before,” says Ernesto Di Mauro at the Institute of Molecular Biology and Pathology in Rome, Italy. “Sometimes it’s the simplest things that people miss.”

Di Mauro and his team repeated the experiment with the same type of borosilicate glass container used in the original experiment and also reran the study with a container made from Teflon. In a third rerun of the experiment, they added glass chips to the Teflon container mixture.

The team speculated that the reactions performed in the presence of glass would generate more complex molecules because glass contains silicates. Silicate can get dissolved and reabsorbed on to the surface of a mixture and so affect what type of reactions occur, says Di Mauro.

Teflon on the other hand, which wasn’t widely used in the 1950s when Miller and Urey ran their experiment, is chemically inert and has no such effect.

Di Mauro’s team found that the glass beaker did indeed contain the most diverse mixture of complex organic reaction products. Meanwhile, the Teflon beaker with glass chips produced fewer complex compounds – probably because the glass chips had a lower combined surface area than the glass beaker itself. There were even fewer complex compounds when the experiment was run in a Teflon beaker with no glass present.

“The glass is like the rocks on Earth – it catalyses the reaction,” says Di Mauro.

More than 90 per cent of Earth’s crust is made up of silicates, and they are also common on planets like Mars, where they may also have helped to catalyse reactions that might be important for the origin of life.

“I’m surprised no one has looked at this before,” says Valentina Erastova at the University of Edinburgh, UK. “I think this study just confirms for me that the Miller-Urey experiments were even smarter than originally envisaged.”

Journal reference: Scientific Reports, DOI: 10.1038/s41598-021-00235-4

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