Mendel-Brno 2000

category image Volume: 17
Issue Number 6, Part 2
June 2000

Electrochemical Impedance Spectroscopy of Native and Denatured DNA

The time dependence of the impedance of the electrode double layer around the potentials of the tensammetric peaks and around the potential of maximum adsorption of native and denatured DNA was studied. With native DNA only one desorption maximum is observed on the C-E curves, denatured DNA yields two maxima. It was shown by Palecek and Brabec that the more positive desorption peak at -1.15 V yielded both by the native and denatured DNA corresponds to the desorption of the sugar - phospate backbone. The more negative peak at -1.4 V which yields only denatured DNA corresponds to the more firmly adsorbed bases. In the potential region of desorption increases the resistivity component of the impedance, which is larger with denatured DNA. This can be explained by the higher flexibility of denatured DNA compared to the native one resulting in the higher dielectric losses by the adsorption - desorption process. At potentials of maximum adsorption (around -0.7 V) the differential capacitance of the double layer decreases with time more fast with denatured DNA then with native DNA due to the higher diffusion coefficient of denatured DNA. From the frequency dependence of the impedance of the electrode double layer we have found that the dielectric losses are higher at the desorption potentials than at the potentials of maximum adsorption. The desorption of denatured DNA is accompanied by higher dielectric losses than the desorption of native DNA. With denatured DNA the desorption of more firmly bound bases is accompanied by higher dielectric losses then the desorption of the sugar-phosphate backbone

Vladimir Vetterl1,2, , Frantisek Jelen1, Viktor Drazan1, Ludek Strasak1, and Stanislav Hason2

1Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno
2Laboratory of Biophysics, Department of Physical Electronics,
Faculty of Sciences Masaryk University, Brno