Researchers have developed a new way to monitor chemical reactions in liquids, shedding light on reactions involving molecules such as urea that may have contributed to the emergence of life on Earth. This technology involves a special device that produces a tiny liquid jet and X-ray spectroscopy, allowing scientists to study reactions that occur in mere femtoseconds.

Scientists from ETH Zurich and the University of Geneva have developed a new technique that allows them to monitor chemical reactions occurring in liquids with extremely high temporal resolution. This innovation enables them to track how the molecules inside change in mere femtoseconds – in other words, within a few quadrillionths of a second.

This achievement builds on previous research by the same team led by Hans-Jacob Werner, professor of physical chemistry at ETH Zurich. This work has yielded results similar to reactions that occur in gaseous environments.

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

Molecular pioneer in biochemistry

Using the new method, the researchers were able to gain insight into the processes that led to the emergence of life on Earth. Many scholars hypothesize that urea played a pivotal role here. It is one of the simplest molecules that contains carbon and nitrogen.

Moreover, it is very likely that urea existed even when the Earth was very young, which was also suggested by a famous experiment carried out in the 1950s: the American scientist Stanley Miller prepared a mixture of those gases which he believed formed the primitive elements of the planet. The atmosphere and its exposure to thunderstorm conditions. This produced a series of molecules, one of which was urea.

According to current theories, urea could have been enriched in warm pools – commonly called primordial soup – on the then lifeless Earth. As the water in this soup evaporated, the urea concentration increased. Through exposure to ionizing radiation such as cosmic rays, this concentrated urea may have produced malonic sour Through multiple synthetic steps. This in turn may have created the building blocks for RNA And DNA.

Why exactly did this reaction occur?

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

It is important to know that the urea molecules present in a concentrated urea solution assemble themselves into pairs, or what are known as dimers. Researchers have now been able to prove that ionizing radiation causes hydrogen corn Within each of these dimers to move from one urea molecule to another. This converts one urea molecule into a protonated urea molecule, and the other into a urea radical. The latter is very chemically reactive – so reactive, in fact, that it will likely react with other molecules, thus also forming malonic acid.

The researchers were also able to show that this transfer of a hydrogen atom occurs very quickly, taking only about 150 femtoseconds, or 150 quadrillionths of a second. “This is so fast that this reaction preempts all the other reactions that could theoretically also occur,” Forner says. “This explains why concentrated urea solutions produce urea radicals rather than hosting other reactions that would produce other molecules.”

Interactions in liquids are of great importance

In the future, Forner and his colleagues want to study 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 their new method, it can also be used more generally to examine the precise sequence of chemical reactions in liquids. “A whole host of important chemical reactions occur in fluids, not only all the biochemical processes in the human body, but also many industrially relevant chemical combinations,” Forner says. “This is why it is so important that we now extend the scope of high-temporal resolution X-ray spectroscopy to include reactions in liquids.”

Reference: “Femtosecond proton transfer in urea solutions investigated by X-ray spectroscopy” by Zhong Yin, Yi-Ping Zhang, Tadas Balciunas, Yashuj Shakya, Alexa Djurovic, Jeffrey Goller, Giuseppe Fazio, Ruben Santra, Ludger Inhester, Jan Pierre Wolff and Hans Jacob Werner, June 28, 2023, nature.
doi: 10.1038/s41586-023-06182-6

Researchers from ETH Zurich and the University of Geneva were assisted in this work by colleagues from Deutsches Elektronen-Synchrotron. Daisy in Hamburg, who performed the necessary calculations to interpret the measurement data.

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