Researchers have used innovative X-ray spectroscopy to understand how ionized urea molecules contribute to the origins of life on Earth, paving the way for advances in atomic chemistry. Above is a representation of photoionization-induced proton transfer between two urea molecules in an aqueous urea solution. Credit: Ludger Inhester

A new technology has provided new insights into a long-standing mystery: How did life originate on Earth?

Before life appeared on our planet, during what researchers refer to as the prebiotic phase, the atmosphere was thinner. This means that high-energy radiation from space was everywhere and ionized particles. Some hypothesize that small pools of water containing urea – an organic compound necessary for the formation of nucleobases – became exposed to this intense radiation, causing the urea to be converted into reaction products. These will serve as the building blocks of life: DNA And RNA.

But to learn more about this process, scientists needed to delve deeper into the mechanism behind urea’s ionization and reaction, as well as the reaction pathways and energy dissipation.

An international collaborative group including corresponding author Zhong Yin, who is currently an associate professor at the International Center for Intelligent Synchrotron Radiation Innovation (SRIS) of Tohoku University, along with colleagues from the University of Geneva (UNIGE) and the ETH Zurich (ETHZ), and the University of Hamburg More can be revealed thanks to an innovative X-ray spectroscopy approach.

This technology, which harnessed a highly harmonic light source and a flat, sub-micron liquid jet, enabled researchers to examine chemical reactions occurring in liquids with unparalleled temporal resolution. Most importantly, this pioneering approach allowed the researchers to investigate complex changes in urea molecules at the femtosecond level, a quadrillionth of a second.

“We showed for the first time how urea molecules interact after ionization,” says Yin. “Ionization radiation destroys the biomolecules of urea. But as the energy from the radiation is dissipated, the urea undergoes a dynamic process that occurs on a femtosecond time scale.

Previous studies examining molecular interactions were limited to the gas phase. In order to extend this to the aquatic environment, the natural environment for biochemical processes, the group had to design a device that could generate an extremely thin liquid jet, less than a millionth of a meter thick, within a vacuum. A thicker plane would have hindered the measurements by absorbing part of the X-rays used.

Yin, who served as the principal experimental researcher, believes their breakthrough does more than just answer how life formed on Earth. It also opens a new path in the new scientific field of atomic chemistry. “Shorter light pulses are essential for understanding chemical reactions in real time and pushing the boundaries in atomic chemistry. Our approach enables scientists to observe the molecular film, following every step of the process along the way.

Reference: “Femtosecond proton transfer in urea solutions investigated by X-ray spectroscopy” by Zhong Yin, Yi-Ping Zhang, Tadas Balciunas, Yashoj 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

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