The numerical models currently used in radiobiology and clinical radiotherapy do not capture the detailed dynamics of these interactions at the atomic level. The interaction of radiation with DNA’s electronic structure is a complex process. Their findings could eventually help to minimize the long-term radiation effects from cancer treatments and human spaceflight. Christopher Shepard of the University of North Carolina at Chapel Hill and his colleagues now use powerful computer simulations to show exactly what part of the DNA molecule receives damaging levels of energy when exposed to charged-particle radiation (Fig. Understanding the mechanisms behind these interactions is critical for developing radiation therapies and improving radiation protection strategies. The interaction of ionizing radiation with tissue and organs can lead to localized energy deposition large enough to instigate double strand breaks in DNA, which can lead to mutations, chromosomal aberrations, and changes in gene expression. Radiobiology studies on the effects of ionizing radiation on human health focus on the deoxyribonucleic acid (DNA) molecule as the primary target for deleterious outcomes. ![]() As a result, radiation that strikes a side chain is more likely to cause damage. The energy transferred when a proton strikes the sugar-phosphate side chain (red) is more than 2 to 3 times larger than that transferred when the proton strikes a nucleobase (turquoise). Adapted by APS/ Alan Stonebraker Figure 1: Simulations that “dissolve” a DNA molecule into its components-water (light blue spheres) nucleobases (dark blue spheres) and sugar-phosphate side chains (magenta spheres)-show that the amount of energy transferred to the molecule by an incoming proton (H+) depends on the part of the DNA molecule that gets hit.
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