Schema des Bestrahlungsexperiments

Oben: Schema des Bestrahlungsexperiments und Komponenten der Probenhalterung für die Bestrahlung von DNA-Lösungen in der Vakuumumgebung des Elektronenmikroskops. Unten: Berechnete Energieverteilung der Sekundärelektronen in Wasser.

Source: Hahn et al. Phys. Chem. Chem. Phys., 2017,19, 1798-1805 (Open access Lizenz: CC BY 3.0)

Direct electron irradiation of DNA in a fully aqueous environment. Damage determination in combination with Monte Carlo simulations

To treat cancer by radiation therapy the tumor has to be destroyed while minimizing the damage to the surrounding healthy tissue. To make radiation therapy more efficient while decreasing detrimental effects on the patient, a better understanding of the underlying molecular processes is needed. Thereby the energy deposit and scattering events in the vicinity to the DNA, the carrier of genetic information, is of interest. The majority of scattering events of the primary high energy radiation in water involve secondary electrons which are produced in copious amounts.

To determine their damaging efficiency a new experimental method was developed, whereby aqueous solutions can be irradiated directly with electrons of variable energy within an electron microscope.

The properties of the irradiated DNA solution can be varied such that realistic physiological conditions are obtained. Electron scattering simulations were used to determine the spatial resolved energy deposit within the liquid volume with nanometer resolution.

Picture of a silicon nitride membrane with pressure

Silicon nitride membrane with pressure, which is separating the vacuum and the liquid. The membrane is transparent to the high energy electrons.

Source: BAM, Division Nanotribology and Nanostructuring of Surfaces

This combination of experimental and simulation methods enables the determination of dose-damage relations for electron irradiation of biological systems under realistic physiological conditions. Important radiation biological parameters, such as the median-lethal dose, where 50% of DNA molecules are damaged, and the ratio of single- to double-strand-breaks were determined as 1.7 Gy and 12:1, respectively.

The presented method is under active development. Currently, experiments with a focus on the influence of the chemical environment on the damage of DNA-protein complexes are performed.

Direct electron irradiation of DNA in fully aqueous environment. Damage determination in combination with Monte Carlo simulations
Marc Benjamin Hahn, Susann Meyer, Maria-Astrid Schröter, H. Seitz, Hans-Jörg Kunte, Tihomir Solomun, Heinz Sturm
Physical Chemistry Chemical Physics (PCCP), Issue 3, 2017
BAM Department Materials and the Environment, Division Biodeterioration and Reference Organisms, Department Materials Protection and Surface Technology, Division Nanotribology and Nanostructuring of Surfaces