241 - Voltammetric studies on the bioelectrochemical behaviour of ultrasound sonicated and γ-irradiated native DNA

Abstract

The effects of ultrasonication treatment and of γ-irradiation damages on the molecular weight and the conformation of native calf thymus DNA have been elucidated by application of sweep voltammetry at a stationary mercury electrode (HMDE). This is a well established approach for the investigation of the hydrodynamic properties and the interfacial behaviour of DNA and other nucleotides at charged interfaces. Below pH 7, the faradaic response, connected with the reduction of protonated adenine and cytosine moieties from those zones of adsorbed native DNA where during the adsorption time t s before the sweep the double helix has opened can be utilized to monitor the sonication and radiation effects on DNA in a twofold manner depending on the fact whether full coverage of the interface with adsorbed DNA had been attained during the adsorption time t s before the sweep, or not. In the first case the reduction response is controlled by the diffusion rate of DNA from the bulk towards the interface electrode¦solution and the evaluated diffusion coefficient of the polynucleotide is correlated to its weight average molecular weight. For ultrasonication a good agreement between diffusion coefficients resulting from voltammetric and sedimentation measurements is observed. The result of sonication is merely a cutting of the native DNA-polymer into smaller analogous parts without affecting significantly its double