A study reveals how urea could be the gateway to life

June 28 () –

Swiss and German researchers have found that urea reacts extremely rapidly under the conditions that existed when our planet was formeda finding that allows us to better understand how life could begin on Earth, as published in the journal ‘Nature’.

Researchers from the ETH Zurich and the University of Geneva in Switzerland, in collaboration with German colleagues, have developed a new method that makes it possible to observe chemical reactions taking place in liquids with extremely high temporal resolution. This means that they can examine how molecules change in just a few femtoseconds, that is, in a few quadrillionths of a second.

The method builds on previous work by the same group of researchers, led by Hans Jakob Wörner, Professor of Physical Chemistry at ETH Zurich, which produced similar results for reactions that take place in gaseous environments.

To extend their X-ray spectroscopy observations to liquids, the researchers had to design an apparatus capable of producing a liquid jet with a diameter of less than one micrometer in a vacuum. This was essential because if the jet were wider, it would absorb some of the X-rays used to measure it.

Thanks to this new method, the researchers were able to better understand the processes that led to the appearance of life on Earth. Many scientists assume that urea played a key role.

It is one of the simplest molecules containing carbon and nitrogen. What’s more, it is very likely that urea was present even when the Earth was very young, something that a famous experiment conducted in the 1950s also suggested: The American scientist Stanley Miller prepared a mixture of the gases that are believed to have formed the early atmosphere of the planet and exposed it to the conditions of a thunderstorm.. The result was a series of molecules, one of which was urea.

According to current theories, the urea could have been enriched in the hot pools — commonly called primordial soup — on Earth then lifeless. As the water in this soup evaporated, the concentration of urea increased. Upon exposure to ionizing radiation such as cosmic rays, it is possible that this concentrated urea produced malonic acid in multiple synthesis steps. In turn, this may have created the building blocks of RNA and DNA.

Using their new method, the researchers from ETH Zurich and the University of Geneva investigated the first step in this long series of chemical reactions to find out how a concentrated urea solution behaves when exposed to ionizing radiation.

The urea molecules in a concentrated urea solution clump together in pairs, or what are known as dimers. As the researchers have now been able to show, ionizing radiation causes a hydrogen atom from each of these dimers to move from one urea molecule to the other. This converts one urea molecule to a protonated urea molecule and the other to a urea radical.. The latter is chemically very reactive, so much so that it is very probable that it reacts with other molecules, also forming malonic acid.

The researchers were also able to show that this transfer of a hydrogen atom occurs extremely quickly, taking only about 150 femtoseconds, or 150 quadrillionths of a second. “It is so fast that this reaction is ahead of all the others that could theoretically also take place. says Wörner. This explains why concentrated urea solutions produce urea radicals rather than harbor other reactions that would produce other molecules.”

In the future, Wörner and his colleagues want to examine the next steps that lead to the formation of malonic acid. They hope this will help them understand the origins of life on Earth.

As for his new method, in general it can also be used to examine the precise sequence of chemical reactions in liquids.

“A whole series of important chemical reactions take place in liquids: not only all biochemical processes in the human body, but also a large number of chemical syntheses relevant to industry. says Wörner. That is why it is so important that we have now extended the scope of high time-resolution X-ray spectroscopy to include reactions in liquids.”