Induction and Repair of DNA Lesions in Cultured Human Melanoma Cells Exposed to a Nitrogen-ion Beam

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Abstract
Induction and repair kinetics of DNA lesions after exposure to nitrogen ions (N-ions) were studied in comparison to those after 180 kVp X-rays. DNA lesions in human melanoma cells (HMV-I) irradiated with 95 MeV N-ions (0–6 Gy, l.e.t.D=530 keV μ−1 or with X-rays (0·9 Gy) were assayed by alkaline elution. The N-ion r.b.e. for DNA lesion induction was approximately 0·7. About 85 per cent of the lesions induced by N ions were rejoined with a time-course similar to the rejoining of DNA lesions produced by X-rays. These lesions were considered to be induced by δ-rays around the N-ion tracks. The fraction of residual DNA lesions remaining after a 6 h post-irradiation incubation was higher for N-ions than for X-rays. Unlike the case for X-rays, DNA-protein crosslinks were included in the residual DNA lesions after N-ion irradiation.