A layer of either synthetic or natural DNA deposited on the gold electrode surface can be specifically excited by UV irradiation under conditions of the presence of dissolved oxygen in the solution. Apparently such irradiation leads to the reversible changes in the rigidity of the DNA layer and the corresponding extent of hydration of the strands. This can be monitored with an electrochemical quartz crystal microbalance, since the regular oscillations appear in the microbalance readout. It was found that the presence of dissolved oxygen is necessary for the start and the continuation of the oscillations, while the UV light is necessary only for the triggering of this phenomenon. The oxygen reactive species formed during the UV irradiation must take part in the cycling process, as the oscillation continues after turning the UV light off. Some voltammetric and CD spectroscopic experiments were also done with the DNA layers to monitor the action of UV radiation. The PAH polymer, that contains no easily oxidized components, was examined for the comparison purpose. (C) 2013 Elsevier Ltd. All rights reserved.