X-ray laser reveals how radiation damage arises

DOUBLE BOMBARDMENT EXPOSES THE DETAILED DYNAMICS OF HOW WATER MOLECULES BREAK APART

An international research team has used the SQS instrument at the European XFEL to gain new insights into how radiation damage occurs in biological tissue. The study reveals in detail how water molecules are broken apart by high-energy radiation, creating potentially hazardous electrically charged ions, which can go on to trigger harmful reactions in the organism. 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 presents its observations and analyses in the scientific journal Physical Review X.

Since water is present in every known organism, the so-called photolysis of water is often the starting point for radiation damage. “However, the chain of reactions that can be triggered in the body by high-energy radiation is still not fully understood,” explains Inhester. “For example, even just observing the formation of individual ions and radicals in water when high-energy radiation is absorbed is already very difficult.”

Read more on the XFEL website

Image: After the absorption of an X-ray photon, the water molecule can bend up so far that after only about ten femtoseconds (quadrillionths of a second) both hydrogen atoms (grey) are facing each other, with the oxygen atom (red) in the middle. This motion can be studied by absorbing a second X-ray photon.

Credit: DESY, Ludger Inhester

Scientists capture a ‘quantum tug’ between neighbouring water molecules

The work sheds light on the web of hydrogen bonds that gives water its strange properties, which play a vital role in many chemical and biological processes.

Water is the most abundant yet least understood liquid in nature. It exhibits many strange behaviors that scientists still struggle to explain. While most liquids get denser as they get colder, water is most dense at 39 degrees Fahrenheit, just above its freezing point. This is why ice floats to the top of a drinking glass and lakes freeze from the surface down, allowing marine life to survive cold winters. Water also has an unusually high surface tension, allowing insects to walk on its surface, and a large capacity to store heat, keeping ocean temperatures stable.

Now, a team that includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Stockholm University in Sweden have made the first direct observation of how hydrogen atoms in water molecules tug and push neighbouring water molecules when they are excited with laser light. Their results, published in Nature today, reveal effects that could underpin key aspects of the microscopic origin of water’s strange properties and could lead to a better understanding of how water helps proteins function in living organisms.

Read more on the LCLS website

Image: For these experiments, the research team (left to right: Xiaozhe Shen, Pedro Nunes, Jie Yang and Xijie Wang) used SLAC’s MeV-UED, a high-speed “electron camera” that uses a powerful beam of electrons to detect subtle molecular movements in samples.

Credit: Dawn Harmer/SLAC National Accelerator Laboratory