Dielectric properties of aqueous solutions of sonicated DNA above 40 MHz

Abstract

SynopsisThe dielectric properties of sonicated calf-thymus DNA sodium salt in aqueous sclutions have been studied in the frequency range from 40 MHz to 2 GHz by time domain spectroscopy (TDS). A dielectric dispersion not previously reported was found, which has a characteristic frequency of about 150 MHz. All of the dielectric parameters are insensitive to the size of DNA fragments and to helix-to-coil transitions. The study of this dispersion as a function of DNA concentration and temperature allows us to conclude that it may be due to counterion fluctuation on short sections, probably in a direction transverse to the macromolecular axis.

Dielectric relaxation measurements of 12 kbp plasmid DNA

“…Previous dielectric spectroscopic investigations of polyelectrolyte solutions, including DNA, have proposed a number of mechanisms for the dispersions. These include Maxwell^Wagner interfacial polarisation [12,17], rotation of bound water molecules [14] and polar groups [11] associated with the DNA, and £uctuations of counterions along the longitudinal [1^7] and transverse [10] axes of the DNA. Although it is di¤cult to draw a de¢nitive conclusion about the mechanism(s), the evidence tends to favour counterion £uctuation along the DNA axis, in particular concerning the low frequency relaxation around 140 kHz.…”