Kinetics of DNA compaction at the electrode surface

Abstract

At the stationary mercury electrode (H.M.D.E.) the fading reactions of a.c. peak 2 of native and of denatured DNA were recorded as functions of the temperature and of the constant potential as well as of the periodical potential sweep over the a.c. peaks 1 and 2. Peak height and peak kinetics were lowered by complex formation of DNA with netropsin. Our preliminary explanation for the fading process is based on the steep rise of the concentration of the cation in the diffuse double—layer with alteration of the potential from prepolarization (coverage of the electrode surface) to the more negative peak potential. This increase of counter cations near to the phosphate groups enhances the flexibility of the attached segments of the strands and, hence, the response to the a.c. field at the electrode surface. The vibration of segments leads to further dehydration and compaction of the molecule and finally to a rigid superstructure like a DNA crystal (native DNA) or a sandwich form (denatured DNA). In this final state the whole peak response disappears. In such a way polarography realizes the possibility of forming thin boundary layers in a reproducible manner. Thereby it can give a model for the regulation of compact nucleic acid connected with partial dehydration of the strands.