Effects of radical scavengers on radiation-induced DNA double strand breaks.
OBJECTIVE
To investigate possible effects of Tris and phenol on the dynamic properties of gamma-irradiated DNA molecules in addition to their well known scavenging capacity.


METHODS
Native and fragmented calf thymus DNA molecules were exposed to various doses of 60Co gamma-rays at approximately 4.5Gy/min. Using thermal transition spectrophotometry, pulsed field gel electrophoresis and standard agarose gel electrophoresis, the effects of Tris, phenol and NaCl on the double helix to single coil thermal transition temperature, Tm, and the yield of the double-strand breaks (Gdsb) of the irradiated DNA molecules have been studied.


RESULTS
DNA molecules exposed to gamma-rays showed a decreased Tm and a corresponding increase of the Gdsb yield. Tris, as well as phenol, exhibited a strong protection against preventing these radiation-induced alterations. In addition, both substances strongly affected the thermal stability of the non-irradiated DNA samples. These results, compared with data obtained by NaCl and its effects on DNA thermostability and Gdsb, revealed that in the presence of both scavengers the observed dsb decrease was correlated to an increased molecular stability of DNA.


CONCLUSIONS
This work suggests that the total protective effect of Tris and phenol against radiation-induced dsb is mainly attributed to their well-known radical scavenging properties, while relatively minor protective effects arise from their contribution to an increased molecular stability of DNA.
Haveles
K S
KS
Institute of Biology, National Center for Scientific Research DEMOKRITOS, Attiki, Greece.
Georgakilas
A G
AG
Sideris
E G
EG
Sophianopoulou
V
V
D000818:Animals; D002417:Cattle; D004247:DNA / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects*; D016521:Electrophoresis, Gel, Pulsed-Field; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005720:Gamma Rays; D009691:Nucleic Acid Denaturation; D019800:Phenol / Q000494:pharmacology; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology; D013053:Spectrophotometry; D014325:Tromethamine / Q000494:pharmacology
D016166:Free Radical Scavengers; D011837:Radiation-Protective Agents; D014325:Tromethamine; D019800:Phenol; D012965:Sodium Chloride; D004247:DNA