Dielectric study of the double helix to single coil transition of DNA

The authors investigated the dielectric behavior of mammalian DNA macromolecules of different sizes in aqueous solution, by dielectric relaxation spectroscopy in the frequency range 100 Hz to 1 MHz, during the double helix to single coil thermal transition, in association with the gradual disruption of the hydrogen bonds between the complementary nitrogenous bases of the DNA double helix, measured by thermal transition spectrophotometry. The authors´ results have shown that, when the temperature of DNA samples is gradually increasing, changes in specific conductivity σ_dc precede changes in A₂₆₀ absorbance at the UV region, where A₂₆₀ is related to the disruption of the hydrogen bonds between the two DNA strands. The presented experimental evidence extends the validation of multistage models for this transition phase to the case of large size mammalian native macromolecular DNA