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.
OBJECTIVE
The major products from polycrystalline purine and pyrimidine DNA nucleotides after low- and high-LET irradiation were investigated quantitatively by HPLC and 1H-NMR spectroscopy.


METHODS
Solid nucleotide samples were either X-irradiated as cylindrical pellets or heavy-ion bombarded (LET range of 100-12,500 keV/microm) as very thin tablets at 300K. Product analysis was performed by HPLC and 1H-NMR.


RESULTS
For TMP the 5,6-dihydroadduct was 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 radiation action. The formation of the products was linear with dose up to 300 kGy for X-irradiation or 200 kGy for heavy-ion bombardment. The estimation of the radiation chemical yields revealed G-values of about 10(-7) mol x J(-1) and were typically smaller for irradiation with charged particles than those 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 nucleotides are comparable in magnitude. The 5,6-dihydroadduct from TMP is a major radiation induced product with larger yields than found for base release after X-irradiation and comparable yields after heavy-ion bombardment. The LET dependence of the G-values for base release in nucleotides is similar and resembles the double strand break formation in DNA. The observed similarity in the LET dependence of the G-values might derive from an inhomogeneous distribution of energy deposition resulting in 'clustered damage'.
Hoffmann
A K
AK
Fachrichtung Biophysik und Physikalische Grundlagen der Medizin, Universität des Saarlandes, Homburg, Germany.
Hüttermann
J
J
D000225:Adenine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003596:Cytosine / Q000737:chemistry; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D018736:DNA Adducts / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006147:Guanine / Q000737:chemistry; D020450:Heavy Ions; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009841:Oligonucleotides / Q000528:radiation effects; D013938:Thymidine Monophosphate / Q000737:chemistry; D014965:X-Rays
D018736:DNA Adducts; D009841:Oligonucleotides; D013938:Thymidine Monophosphate; D006147:Guanine; D003596:Cytosine; D004247:DNA; D000225:Adenine