A new electrochemical approach for the in vitro investigation of damage in native DNA by small gamma-radiation doses

Mercury Electrodes in Nucleic Acid Electrochemistry: Sensitive Analytical Tools and Probes of DNA Structure. A Review

This review is devoted to applications of mercury electrodes in the electrochemical analysis of nucleic acids and in studies of DNA structure and interactions. At the mercury electrodes, nucleic acids yield faradaic signals due to redox processes involving adenine, cytosine and guanine residues, and tensammetric signals due to adsorption/desorption of polynucleotide chains at the electrode surface. Some of these signals are highly sensitive to DNA structure, providing information about conformation changes of the DNA double helix, formation of DNA strand breaks as well as covalent or non-covalent DNA interactions with small molecules (including genotoxic agents, drugs, etc.). Measurements at mercury electrodes allow for determination of small quantities of unmodified or electrochemically labeled nucleic acids. DNA-modified mercury electrodes have been used as biodetectors for DNA damaging agents or as detection electrodes in DNA hybridization assays. Mercury film and solid amalgam electrodes possess similar features in the nucleic acid analysis to mercury drop electrodes. On the contrary, intrinsic (label-free) DNA electrochemical responses at other (non-mercury) solid electrodes cannot provide information about small changes of the DNA structure. A review with 188 references.

Effect of gamma-irradiation on the conformation of the native DNA molecule

Extensive investigation of gamma-irradiated DNA solutions with the application of several informative physical methods suggested that at doses of 10-30 Gy the observed change in the size of the DNA molecule is due to a decrease in long-range interactions in the macromolecule. The comparison of the results of investigations of non-irradiated and irradiated DNA and its complexes with low molecular weight ligands over a wide range of ionic strengths showed that these interactions are electrostatic in nature and are due to a decrease in the charge density on the DNA molecule when its solutions are irradiated. In the irradiation dose range discussed here, the persistent length of the DNA molecule determined by short-range interactions in the chain does not undergo pronounced changes. It is shown that the free ligand in the irradiated solution can protect the DNA molecule against radiation damage. In contrast, the ligand bonded by intercalation does not exhibit this ability.