The relation between the polarographic behaviour of DNA and its conformation in solution

Abstract

1. The behaviour of native and denatured DNA relative to pH, type and concentration of salts in solution and other parameters was studied with the aid of direct and alternating current polarography and pulse polarography. 2. It was found that the height of the pulse-polarographic wave of denatured DNA is within a certain pH range, independent of pH and salt concentration. 3. In the medium where the polarographic current value does not depend on pH and salt concentration ( e.g. in 1.0 M ammonium formate, pH 6), the polarographic current of denatured DNA is directly proportional to the square root of the height of the mercury column. This dependence is characteristic for diffusion-controlled currents. The same dependence is displayed by native DNA. 4. In a suitably chosen medium it is possible to observe a correlation between the conformation of the polynucleotide and its polarographic reducibility. Under conditions where pH, type and concentration of salts strongly influence the electrode processes ( e.g. at low salt concentration and/or alkaline pH) this correlation may be obscured. Doubts about the existence of a relationship between the polarographic behaviour of DNA and its conformation in solution, arising from the recently published paper by J. Filipski, J. Chmielowski and M. Chorazy ( Biochim. Biophys. Acta, 232 (1971) 451), were based primarily on the results of the polarographic measurements of these authors, which in our opinion were not performed under the most suitable conditions.