Research Unit for Analysis by Nuclear Reactions (LARN)
The experts
Prof. Stéphane Lucas
Prof. Anne-Catherine Heuskin
Dr. Sébastien Penninckx
Ing. Richard Coos
Expertise in irradiation
With the help of a multidisciplinary team, we study cell response to photon or particle irradiation theoretically as well as experimentally.
The UNamur particle accelerator (Tandetron Linear Accelerator – ALTAÏS) and the RX irradiator enable in-vitro irradiations of rotifers with protons, He+ and Li+ ions, carbon ions (hadrontherapy) or photons. Numerous experimental methods, among which RMN spectroscopy, enable to evaluate the effects of radiation and are supported by simulations involving the MCNPx and GEANT4 codes.
ALTAÏS is a 2 MV Tandem accelerator which was installed at the LARN laboratory in 1999. Originally, it was designed for material analysis experiments. A schematic representation is given in the figure.
The first part consists of a dual source which can produce any ion from hydrogen to uranium. The negative ion beam is then extracted from the source and deflected to the main tube with the low energy magnet, whose resolution is better than 1 uma. The Faraday cup and the BPM (Beam Profile Monitor) allow tuning the beam intensity and shape with the aid of upstream electrostatic lenses.
The acceleration is carried out in two parts, hence the name Tandetron. First, the negative ions are attracted to the positive high voltage and the stripper channel located in the center of the tube. Here, ions can be stripped from negative to positive ions and are then repelled by the positive voltage to the end of the tube. A high-energy magnet is used to deflect the beam in one of the beam lines, according to the particle energy, mass and charge.
DNA damage
Contrary to proteins, which are also affected by ionizing radiation but are present in numerous amount, only one copy of DNA is present in the cell nucleus. Because the DNA contains all the genetic information, any damage to the structure could be harmful and potentially lethal for the cell. A cell still harboring too much DNA damage when entering mitosis is likely to die.
Single strand breaks occur when the phosphate backbone is broken on one side of the DNA helix, whereas double strand breaks involve the breakage of the two opposite sides of the DNA helix. While single strand breaks are easy to handle, because a template for repair is available on the other side of the helix, double strand breaks are more harmful and repair often introduce mutations. Other lesions, such as base damages, abasic sites, damaged sugars or DNA-protein crosslinks are also produced. A difference arises when switching from uncharged (e.g. X-ray) or charged (e.g. proton) particle as radiation source. Most of the time, X-rays generate simple lesions, such as single strand breaks or base damage, because ionization they produce are less dense, less gathered together. Hence, damage produced by X-rays are less severe and easier to repair. However, when charged particles such as protons are used, locally multiply damage sites arise. These clustered lesions, concentrated in a localized region of the DNA, are even more difficult to repair and often lead to cell death. This is due to the high ionization density occurring on the proton path.
Galactic cosmic rays (a variety of densely ionizing radiations no limited to protons) are encountered in space and impair space exploration.
Anne-Catherine explains DNA repair
Related publications
Considering Cell Proliferation to Optimize Detection of Radiation-Induced 53BP1-Positive Foci in 15 Mouse Strains Ex Vivo – Sébastien Penninckx, Eloise Pariset, Ana Uriarte Acuna, Stéphane Lucas & Sylvain V. Costes
53BP1 Repair Kinetics for Prediction of In Vivo Radiation Susceptibility in 15 Mouse Strains – Eloise Pariset, Sébastien Penninckx, Charlotte Degorre Kerbaul, Elodie Guiet, Alejandra Lopez Macha, Egle Cekanaviciute, Antoine M. Snijders, Jian-Hua Mao, François Paris & Sylvain V. Costes
Dose, LET and Strain Dependence of Radiation-Induced 53BP1 Foci in 15 Mouse Strains Ex Vivo Introducing Novel DNA Damage Metrics – Sébastien Penninckx, Egle Cekanaviciute, Charlotte Degorre, Elodie Guiet, Louise Viger, Stéphane Lucas & Sylvain V. Costes
Combinatorial DNA Damage Pairing Model Based on X-Ray-Induced Foci Predicts the Dose and LET Dependence of Cell Death in Human Breast Cells – Nikhil Vadhavkar, Christopher Pham, Walter Georgescu, Thomas Deschamps, Anne-Catherine Heuskin, Jonathan Tang & Sylvain V. Costes
Toward computer simulation of high-LET in vitro survival curves – A-C Heuskin, C Michiels & S. Lucas
Simulating Space Radiation-Induced Breast Tumor Incidence Using Automata – A.C. Heuskin, A.I. Osseiran, J. Tang, S.V. Costes