Published on 23 July 2019
Research
Transient absorption profiles of pure diethylene glycol and ribothymidine solutions under ambient conditions.

Mehran Mostafavi is a researcher at the Physical Chemistry Laboratory (LCP - CNRS/Université Paris-Sud) and is interested in the synthesis and properties of nanosystems as well as in chemistry under ionizing radiation and ultrafast reactions. His recent work sheds light on the breaks in DNA bases caused by electron attack and the importance of solvent.

Within the Physical Chemistry Laboratory (LCP - CNRS/Université Paris-Sud), Mehran Mostafavi is in charge of the "Elementary Chemical Acts in Condensed Phase" team. This team has been working for many years on electron transfer phenomena in solution using nanosystems. These transfers are very fast, in the femtosecond or picosecond range (10-15 to 10-12 seconds), which makes them very complex to measure.

To stimulate the molecules, Mehran Mostafavi's team accelerates the electrons and directs them to solutions containing the species to be studied. Originally, the team specialized in the study of inorganic systems. "Previously, we didn't work on biological systems at all. But thanks to conferences, I have noticed that there are many studies of electron attacks on DNA bases," he says. This work showed that with a certain amount of kinetic energy supplied to electrons, DNA bases broke. This offers many possibilities in terms of medical applications.

However, Mehran Mostafavi and his collaborators raised some restrictions: most of the studies were conducted in the gas phase and the deductions made were not quite complete. With this preamble, the team set up a series of experiments to study the role of electron solvation in order to determine whether solvated electrons act in the same way as those that are not. They have demonstrated for the first time that electrons before solvation induce a breakage of the bonds composing DNA bases.

They have also conducted other studies on the influence of the solvent. The use of water, to get closer to biological systems, is constraining for the analysis because it very easily induces a dissipation of energy as heat. The use of a less heat loss friendly solvent, such as diethylene glycol, facilitates the attack of DNA bases by unsolvated electrons.

Thanks to collaborations with research teams based in the United States and Japan, the researchers carried out complementary experiments to verify the measurements made in France. Mostafavi says: "Science is global and worldwide, collaborations are always very rewarding. »

Obtaining these results and publishing them was a long-term task: the systems previously studied in the team were mainly inorganic and the experiments carried out were very sophisticated and not routine, so the measurements had to be adapted. "In research, we have some hard times, but we have to persevere. We must be confident and above all analyse each result, as for this article", concludes Mehran Mostafavi.

Jun Ma, Anil Kumar, Yusa Muroya, Shinichi Yamashita, Tsuneaki Sakurai, Sergey A. Denisov, Michael D. Sevilla, Amitava Adhikary, Shu Seki & Mehran Mostafavi. Observation of dissociative quasi-free electron attachment to nucleoside via excited anion radical in solution. Nature Communications 10, Article number: 102 (2019).

 


Mehran Mostafavi

Mehran Mostafavi studied at Orsay University in physical chemistry before completing his thesis under the supervision of Jacqueline Belloni. After a year in a company to promote the results of his thesis, he joined CNRS as a research fellow. Later, he passed the competition to become a university professor at the Physical Chemistry Laboratory (LCP) in Orsay. He is also Scientific Assistant Director at CNRS in charge of Major Research Infrastructures at CNRS Institute of Chemistry.