Studies on the Chemical Interactions of Nitrofurazone with Nucleic Acids during Ɣ-Irradiation

Abstract

<p>Nitrofurazone (NF) alters the radiation chemistry of nucleic acids in hypoxic aqueous solution. (¹⁴C_NF), labelled in the semicarbazone moiety, was found to bind in a stable, covalent manner to DNA, maximum binding occurring under hypoxic conditions. The nuclease plus alkaline phosphatase hydrolysate of the products formed with ¹⁴C- NF and DNA, t-RNA, poly C, and poly U were analysed on a cation exchange column (AG 50WX4) and on an anion exchange column (Sephadex DEAE A25). The mobilities of the adducts on these columns suggested that they are neutral and acidic compounds. Analysis of the nucleoside digest of (¹⁴C- NF )-poiy U, adducts on DEAE anion exchange paper (with and without borate) indicated that these products lack an intact ribose moiety. Analysis of the nucleositle and nucleotide digests of (¹⁴C-NF)-poly U adducts by paper chromatography indicated nucleotide-like products(according to its chromatographic behaviour), and acidic products which appeared to be different from bases, nucleosides or nucleotides. Similar analysis of uracil, uridine, and 5'UMP after exposure to Ɣ-rays in the presence of ¹⁴C- NF, suggested nucleotide-like products with the NF molecule bound to the uracil base.</p> <p>Experiments with (³H-Me)thymidine-DNA and (³H-Me) thymidine showed the existance of thymine derivatives or break-down products which did not contain radioactivity from the ¹⁴C-NF. Paper chromatograpy of (2-¹⁴C)uracil radiolysis products formed with and without NF showed NF to enhance the yield of a compound tentatively identified as uracil glycol. It is concluded that hydrolysates of the products formed when ¹⁴C-NF reacts with irradiated polynucleotides consist of a large number of compounds which contain ¹⁴C and are therefore likely to be adducts. These can readily be separated from the normal nucleosides which are also present but not from radiolysis products. Thus the analytical problem of isolating pure adduct remains a formidable one.</p> <p>The ability of NF to increase single-strand break (SSB) production Ɣ-irradiated λDNA was demonstrated and compared to NF binding to λDNA. Values of 0.64-1.08 were found for the ratio of SSB / NF molecule bound.</p>