Kinetic behavior of the reaction between hydroxyl radical and the SV40 minichromosome

Aqueous solutions containing the minichromosomal form of the virus SV40 and the radical scavenger DMSO were subjected to γ-irradiation, and the resulting formation of single-strand breaks (SSB) was quantified. Under the irradiation conditions, most SSBs were produced as a consequence of hydroxyl radical (OH) reactions. By controlling the competition between DMSO and the viral DNA substrate for OH, we are able to estimate the rate coefficient for the reaction of OH with the SV40 minichromosome. The results cannot be described adequately by homogeneous competition kinetics, but it is possible to describe the rate coefficient for the reaction as a function of the scavenging capacity of the solution. The experimentally determined rate coefficient lies in the range 1×10⁹–2×10⁹ L mol^?1 s^?1 at 10⁷ s^?1, and increases with increasing scavenging capacity.