How urea may have been the gateway to life

Date:
June 28, 2023
Source:
ETH Zurich
Summary:
Urea reacts extremely quickly under the conditions that existed
when our planet was newly formed. This new insight furthers our
understanding of how life on Earth might have begun.


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FULL STORY ========================================================================== Researchers from ETH Zurich and the University of Geneva have developed a
new method that allows them to observe chemical reactions taking place in liquids at extremely high temporal resolution. This means they can examine
how molecules change within just a few femtoseconds -- in other words,
within a few quadrillionths of a second. The method is based on earlier
work done by the same group of researchers led by Hans Jakob Wo"rner,
Professor of Physical Chemistry at ETH Zurich. That work yielded similar results for reactions that take place in gas environments.

To expand 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 micrometre in a vacuum. This was
essential because if the jet were any 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 insights into the processes that led to the emergence
of life on Earth. Many scientists assume that urea played a pivotal
role here. It is one of the simplest molecules containing both carbon
and nitrogen. What's more, it's highly likely that urea was present
even when the Earth was very young, something that was also suggested
by a famous experiment done in the 1950s: American scientist Stanley
Miller concocted a mixture of those gases believed to have made up the
planet's primordial atmosphere and exposed it to the conditions of a thunderstorm. This produced a series of molecules, one of which was urea.

According to current theories, the urea could have become enriched in
warm puddles -- commonly called primordial soup -- on the then lifeless
Earth. As the water in this soup evaporated, the concentration of urea increased. Through exposure to ionising radiation such as cosmic rays,
it's possible that this concentrated urea produced malonic acid over
multiple synthesis steps. In turn, this may have created the building
blocks of RNA and DNA.

Why this exact reaction tool place 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 ionising radiation.

It's important to know that the urea molecules in a concentrated urea
solution group themselves into pairs, or what are known as dimers. As
the researchers have now been able to show, ionising radiation causes
a hydrogen atom within each of these dimers to move from one urea
molecule to the other. This turns one urea molecule into a protonated
urea molecule, and the other into a urea radical. The latter is highly chemically reactive -- so reactive, in fact, that it's very likely to
react with other molecules, thereby also forming malonic acid.

The researchers also managed to show that this transfer of a hydrogen
atom happens extremely quickly, taking only around 150 femtoseconds,
or 150 quadrillionths of a second. "That's so fast that this reaction
preempts all other reactions that might theoretically also take place,"
Wo"rner says. "This explains why concentrated urea solutions produce
urea radicals rather than hosting other reactions that would produce
other molecules." Reactions in liquids are highly relevant In the
future, Wo"rner and his colleagues want to examine the next steps that
lead to the formation of malonic acid. They hope this will help them to understand the origins of life on Earth.

As for their new method, it can also generally be used to examine
the precise sequence of chemical reactions in liquids. "A whole host
of important chemical reactions take place in liquids -- not just all biochemical processes in the human body, but also a great many chemical syntheses relevant to industry," Wo"rner says. "This is why it's so
important that we have now expanded the scope of X-ray spectroscopy
at high temporal resolution to include reactions in liquids." The
researchers from ETH Zurich and the University of Geneva were assisted
in this work by colleagues from Deutsches Elektronen-Synchrotron DESY
in Hamburg, who performed calculations required to interpret measurement
data.

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========================================================================== Story Source: Materials provided by ETH_Zurich. Original written by
Fabio Bergamin. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zhong Yin, Yi-Ping Chang, Tadas Balčiūnas, Yashoj Shakya,
Aleksa Djorović, Geoffrey Gaulier, Giuseppe Fazio,
Robin Santra, Ludger Inhester, Jean-Pierre Wolf, Hans Jakob
Wo"rner. Femtosecond proton transfer in urea solutions probed by
X-ray spectroscopy. Nature, 2023; DOI: 10.1038/s41586-023-06182-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230628130358.htm

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