The invariance of the total direct DNA strand break yield

Abstract

The SSB generation process is homogeneous and independent of the LET of the particles involved, at least within the proton and alpha particle energy range here studied. The target-hit probability is only determined by the ratio between the total volume occupied by targets and that of the ROI where the radiation deposits its energy. The maximum separation distance between two adjacent SSBs to produce a DSB is the parameter that breaks the homogeneity of the target-hit process, making the DSB production process strongly heterogeneous.

Review of Geant4-DNA applications for micro and nanoscale simulations

“…This simplified nucleus was irradiated with incident protons and the authors confirmed the weak dependence of the total strand break yields with incident particle LET, as already observed in [50]. The DSB yield was found to be strongly dependent on LET.…”

“…Irradiating a total of 900 fragments of such chromatin fibres with incident protons and alpha particles in the 0.5 -10 MeV range, the authors could demonstrate that the total strand break yield and the number of energy deposition events required to reach a certain absorbed dose were found nearly independent of the type and energy of the incident ion. The SSB generation process was found to be homogeneous, depending neither on the structure of the DNA nor on the LET of the particles involved, while the DSB yield was found strongly dependent on the LET of the incident radiation [50].…”

“…Bernal et al [50] proposed the first combination of Geant4-DNA physics modelling in liquid water with a geometrical description of DNA based on previous simulations performed with the PENELOPE Monte Carlo code [51,52]. The DNA double helix is represented as a series of slices in the B-DNA conformation, each of them including two phosphodiester groups bound by a complementary base pair (bp).…”

“…Their study on iodine isotopes used two geometrical implementations of 41 base pairs in the B-DNA conformation, the first being similar to the one proposed by Bernal et al [50], the second having a finer granularity. For the first time with Geant4-DNA, they also included a method using a liquid water virtual cylinder around the DNA for the recording of indirect effects, initially proposed by Pomplun [58] and using prototype radiolysis simulation capabilities available in Geant4-DNA.…”

Recent Developments in Geant4

“…A variety of applications based on GEANT4-DNA processes and models allow the study of elementary energy deposition patterns at the sub-cellular scale. For example, the comparison of dose point kernels [114], S-values [115], radial doses [116], cluster patterns for ions with the same LET [117], the effect of a magnetic field on electron track structures [118], and the modeling of direct DNA damage [119][120][121][122] have so far been explored utilizing these tools. They even provide a framework for the future study of non-targeted biological effects [123], extending further the first applications of GEANT4 electromagnetic physics at the physics-biology frontier [124][125][126][127][128][129][130].…”