Purpose: To compare experimental yields of single strand breaks (SSB) and d
ouble strand breaks (DSB) induced in plasmid DNA in aqueous solution by alp
ha -particles and Al-K ultrasoft X-rays (USX) with the corresponding yields
, generated via computer simulations, for a range of mean diffusion distanc
es of the hydroxyl radical ((OH)-O-circle).
Materials and methods: Aerobic, aqueous solutions of plasmid DNA were irrad
iated at 277K with Pu-238 alpha -particles or USX in the presence of 10(-4)
to 0.33 mol dm(-3) Tris and the yields of SSB and DSB determined by gel el
ectrophoresis. Computer simulations, using Monte Carlo track-structure code
s for 1.3 keV electrons (CPA100) and 3.2 MeV alpha -particle track segments
(PITS), were used to obtain yields of DNA SSB and DSB at different (OH)-O-
circle scavenger conditions.
Results: The experimental yield of SSB and DSB induced by AlK USX and SSB i
nduced by alpha -particles and the dependences on the mean diffusion distan
ce of the (OH)-O-circle are in reasonable agreement with the corresponding
simulated yields and their corresponding dependences. However, for DSB indu
ced by alpha -particles, a significant systematic difference exists between
the simulated and experimental yields over the full (OH)-O-circle scavengi
ng range, with the simulated yields being a factor of two to three greater
than the experimental values.
Conclusion: That the simulated yields of strand breaks are generally in rea
sonable agreement with those determined experimentally over a wide range of
(OH)-O-circle scavenging capacities, increases confidence in the use of th
ese simulations as a valuable source of quantitative, mechanistic informati
on on DNA damage induced at very low radiation doses.