| Autor: |
Milligan, J. R., Aguilera, J. A., Nguyen, J. V., Ward, J. F. |
| Předmět: |
|
| Zdroj: |
International Journal of Radiation Biology; Mar2001, Vol. 77 Issue 3, p281-293, 13p, 1 Diagram, 2 Charts, 6 Graphs |
| Abstrakt: |
Purpose: It has been previously argued that γ-irradiation of plasmid DNA in the presence of thiocyanate ions produces products recognized by the E. coli base excision-repair endonuclease formamidopyrimidine-DNA N-glycosylase (FPG), and there that derive from an intermediate guanyl radical species. The wish was to characterize the reactivity of this intermediate with reducing agents. Materials and methods: Aqueous solutions of plasmid DNA containing either bromide or thiocyanate (10[sup -3] to 10[sup -1] mol dm[sup -3]) and also one of six other additives (azide, ferrocyanide, iodide, nitrite, promethazine, tryptophan, 10[sup -7] to 10[sup -3] mol dm[sup -3]) were subjected to [sup 137]Cs γ-irradiation (662 keV). After irradiation, the plasmid was incubated with FPG. Strand break yields before and after incubation were determined by agarose gel electrophoresis under neutral conditions. Results: The very high yields of FPG-sensitive sites in the presence of SCN[sup -] or Br[sup -] decreased significantly with increasing concentrations of all of the six additives, with promethazine and tryptophan being the most efficient additives, and azide and iodide the least. Conclusions: From the results it is possible to estimate values of the rate constants for the reduction of the DNA guanyl radical (5x10[sup 5], 2x10[sup 5], 10[sup 7] and 10[sup 7] dm[sup 3] mol[sup -1] s[sup -1] for ferrocyanide, nitrite, promethazine and tryptophan respectively). [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
