Products from polycrystalline DNA constituents after X-irradiation and heavy-ion bombardment: Formation of the 5,6-dihydroadduct in thymidine 5 '-monophosphate and release of unaltered bases in nucleotides
Ak. Hoffmann et J. Huttermann, Products from polycrystalline DNA constituents after X-irradiation and heavy-ion bombardment: Formation of the 5,6-dihydroadduct in thymidine 5 '-monophosphate and release of unaltered bases in nucleotides, INT J RAD B, 76(9), 2000, pp. 1167-1178
Purpose: The major products from polycrystalline purine and pyrimidine DNA
nucleotides after low- and high-LET irradiation were investigated quantitat
ively by HPLC and H-1-NMR spectroscopy.
Materials and methods: Solid nucleotide samples were either X-irradiated as
cylindrical pellets or heavy-ion bombarded (LET range of 100-12500 keV/mu
m) as very thin tablets at 300K. Product analysis was performed by HPLC and
H-1-NMR.
Results: For TMP the 5,6-dihydroadduct as found to be formed as product of
electron reaction. In addition, all four DNA nucleotides showed a radiation
-induced base release, which is probably connected with the oxidative radia
tion action. The formation of the products was linear with dose up to 300 k
Gy for X-irradiation or 200 kGy for heavy-ion bombardment. The estimation o
f the radiation chemical yields revealed G-values of about 10(-7) molJ(-1)
and were typically smaller for irradiation with charged particles than thos
e for X-rays. After heavy-ion bombardment the G-values first increased with
increasing LET and decreased for very heavy ions.
Conclusions: The yields for base release from both purine and pyrimidine nu
cleotides are comparable in magnitude. The 5,6-dihydroadduct from TMP is a
major radiation induced product with larger yields than found for base rele
ase after X-irradiation and comparable yields after heavy-ion bombardment.
The LET dependence of the G-values for base release in nucleotides is simil
ar and resembles the double strand break formation in DNA. The observed sim
ilarity in the LET dependence of the G-values might derive from an inhomoge
neous distribution of energy deposition resulting in 'clustered damage'.