DNA Conformational Transitions at Different Concentrations and Temperatures Monitored by EIS

We present an EIS study and its analysis to determine the conformational behavior of DNA calf-thymus (13 kbp). The study is carried out at open circuit potential at a pH of 7.3. The results are interpreted in terms of the adsorption impedance theory by using an equivalent circuit approach similar to the one proposed by Frumkin-Melik-Gaikazyan-Randles. All equivalent circuit parameters are inspected as a function of DNA concentrations where it is possible to identify two transitions on the double-layer structure at DNA ca. 0.33 +/- 0.07 and 1.50 mg/mL related to the overlap, C*, and entanglement, C-e, concentrations. (c) 2012 The Electrochemical Society. All rights reserved.