The role of the ascorbate/Cu(II) system on the formation of strand breaks in poly(adenylic acid) (polyA), was studied by conductivity measurements in aqueous solution at pH 7.2 and 3.5 under aerobic conditions. Solutions of poly(adenylic acid) were incubated with freshly prepared ascorbate/Cu(II) solutions at various temperatures and the resulting conductivity increases were followed by measuring the conductivities of the solution at different time intervals. The apparent activation energies for the strand breakage were found from the conductivity measurements to be 59.8 and 22.4 kJ mol(-1) for pH 7.2 and 3.5, respectively.