A research team from around the world utilized the European X-ray laser XFEL to gain a new understanding of the damage caused by radiation to biological tissues. The study reveals in detail how water molecules are ripped into pieces by high-energy radiation, creating potentially hazardous radicals and electrically charged ions, which can go on to cause harmful reactions in the body. The team, led by Maria Novella Piancastelli and Renaud Guillemin from the Sorbonne in Paris, Ludger Inhester from DESY and Till Jahnke from European XFEL is presenting its observations and analysis in the journal of science Physical Review X.
Water is found in all living organisms. Radiation damage often starts with the breaking of H 2O of the water molecule by radiation.
However, the chain of reactions that can be initiated in the body by high-energy radiation are not completely understood. It is difficult to discern the formation of individual chargedions and reactive radicals in water after high-energy radiation is taken in.
Ludger Inhester of DESY
To investigate the sequence of events, researchers aimed the intense pulses of the X-ray laser towards the water vapour. Water molecules typically break down after the absorption of a single high-energy photon from the X-ray. Inhester reports that water molecules were able to absorb not just one but two or more Xray photons, before their debris exploded, thanks to the intense pulses of the Xray laser. Researchers gain a glimpse of the inner workings of molecules after it absorbs an Xray photon.
“The movement of the molecule between two absorption events leave an obvious fingerprint, which means its fragments split in a specific, characteristic way,” says Piancastelli. “We were able to draw conclusions from the ultra-fast dynamics following the water molecule absorbed the first Xray light by taking a close look at the fingerprint and executing sophisticated simulations. The team measured the direction in which the fragments travelled and their speed with a microscope called a reaction. Scientists were able to record the process of disintegration within the water molecule for a few seconds (quadrillionths) with the microscope of a reaction.
It is discovered that the process of getting rid of the water molecule its atoms is much more complicated than we initially thought. The water molecule H 2O begins to expand and stretch, before finally breaking apart. After only ten femtoseconds, the two hydrogen atoms (H) which are usually joined to the oxygen atom (O) at an angle of 104 degrees, could create so much momentum as to meet at an angle of about 180 degrees. This means that the oxygen atom is not actually thrown away when the molecule breaks up due to the fact that the momenta of the two hydrogen nuclei largely are in balance as they fly off leaving the oxygen at rest in the middle. This free oxygen radical can quickly trigger other potentially dangerous chemical reactions in an aqueous atmosphere.
“In our research, it was possible for the first time to take a closer look at the dynamics of a liquid-based molecule after it absorbs high-energy radio radiation,” Inhester, who works at Centre for Free-Electron Laser Science, a collaboration between DESY and the University of Hamburg. “In particular we were able to identifying the formation of the oxygen radicals and hydrogen ions more precisely, as well as how this process develops over time. The breakdown of the water molecule is an important initial step in the chain of reactions that ultimately cause radiation damage.”
The study adds to the overall picture of the effects of radiation on water. A previous study that was conducted by members of the same group had examined the dynamics of the formation of free radicals, also known as free radicals, by less energetic radiation in water. The processes that were observed in this study have the same dynamics as the secondary processes involved in absorption of high-energy radiation currently being studied. The new findings provide answers to fundamental questions about reaction dynamics in water, which are to be further explored at the Centre for Molecular Water Science (CMWS) currently being established with international partners at DESY.
The first tests on single water molecules were carried out with the new COLTRIMS reaction microscope at SQS which is the European XFEL. Jahnke states that the results demonstrated that we can also study complex molecules, such as ethanol and other solvents. This is a great benefit for chemistry.
Researchers from the universities of Frankfurt am Main and Hamburg, Hamburg, Kassel, as well as Gothenburg and Uppsala (Sweden and Finland), from the Fritz Haber Institute of Nuclear Physics and the Max Planck Institute for Nuclear Physics in the USA, Lawrence Berkeley National Laboratory, Kansas State University in Kansas as well as the National Research Council, and the Technical University of Milan, Italy, the Sorbonne, European XFEL, and DESY were also involved in the study.
Jahnke, T., et al. (2021) Inner-Shell-Ionization-Induced Femtosecond Structural Dynamics of Water Molecules Imaged at an X-Ray Free-Electron Laser. Physical Review X. doi.org/10.1103/PhysRevX.11.041044.
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