Aspects of γ-radiation induced modification of calf thymus DNA in the presence of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulfonate and its transition metal complexes with Cu2+ and Ni2+

Radiation-induced double-strand modification of DNA was studied in the absence and presence of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulfonate (NaQSH(2)) and its metal (Cu2+ and Ni2+) complexes in aerated, de-aerated (Argon saturated) and N2O saturated aqueous media at pH 7.4. Ethidium bromide, an established DNA intercalator was used to estimate DNA remaining after interaction with gamma-radiation, by measuring loss of fluorescence of the ethidium bromide-DNA adduct. In de-aerated (Argon saturated) and N2O saturated aqueous media radiation-induced double-strand modification of calf thymus DNA was comparatively less in presence of NaQSH(2) and its Ni(II) complex than standard control indicating the compounds behaved as radio-protectors. However, in presence of the Cu(II) complex radiation-induced double-strand modification increased significantly. In N2O saturated medium, double-strand modification of DNA was almost double in all cases than that observed in de-aerated (Argon saturated) medium indicating (OH)-O-center dot radicals played a major role in modifying DNA. That center dot OH radicals were important was verified by repeating experiments using tertiary-butanol that showed significant decrease in DNA modification. Another important observation was in aerated medium NaQSH(2), Ni(II)-NaQSH(2) did not show radioprotection while Cu(II)-NaQSH(2) was an almost equally effective radiosensitizer as that observed in N2O saturated medium. Role of molecular oxygen as radiosensitizer was thus realized. (C) 2013 Elsevier Ltd. All rights reserved.