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1 January 2000 Protection against Radiation-Induced Degradation of DNA Bases by Polyamines
Thierry Douki, Yann Bretonniere, Jean Cadet
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Douki, T., Bretonniere, Y. and Cadet., K. Protection against Radiation-Induced Degradation of DNA Bases by Polyamines.

Polyamines have been reported to protect DNA against the formation of radiation-induced strand breaks and crosslinks to proteins. The present study was aimed at investigating the protective effect of spermine, spermidine and putrescine against the degradation of DNA bases upon exposure to γ rays in aerated aqueous solution. The yield of 8-oxo-7,8-dihydroguanine and 5-hydroxycytosine was found to decrease for concentrations of spermine and spermidine greater than 0.1 mM. A protection factor of 10 was observed for a concentration of 1 mM of the latter two polyamines. Putrescine afforded a lower protection. In addition, the formation yield of a series of radiation-induced degradation products of the purine and pyrimidine bases was determined within DNA in the presence or absence of spermine. The protection factor was within the same range for all the lesions measured. The latter observation ruled out the possibility of degradation of DNA by radiation-induced polyamine peroxyl radicals. This was confirmed by studies involving radiolysis of DMSO and decomposition of 2,2′-azobis(2-methyl-propionamidine) as sources of alkylperoxyl radicals. Therefore, it is likely that the polyamine-mediated protection against the radiation-induced degradation of DNA bases is due to the compaction of the DNA structure and the reduction in the accessibility of DNA to ˙OH rather than by scavenging ˙OH in the bulk solution or in the vicinity of the DNA.

Thierry Douki, Yann Bretonniere, and Jean Cadet "Protection against Radiation-Induced Degradation of DNA Bases by Polyamines," Radiation Research 153(1), 29-35, (1 January 2000).[0029:PARIDO]2.0.CO;2
Received: 14 June 1999; Accepted: 1 September 1999; Published: 1 January 2000
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