Radiation-induced luminescence from 'dry' and hydrated DNA and related macromolecules

The radiation-induced luminescence from three types of fibrous DNA and a series of polydeoxynucleotides was measured under vacuum or in the presence of oxygen at 77 and 293 K. The in-pulse emission spectra, generated by electrons with energies less than 260 keV, have been investigated in order to obtain an understanding of the effects of direct energy disposition within DNA. The in-pulse emission characteristics of DNA and the polydeoxynucleotides were found to be independent of both temperature and the presence of oxygen. Investigations were extended to study the effect of hydration of DNA upon the resulting radiation induced emission spectra. It is apparent that with DNA thin film (15-20 mu m) containing greater than 50% water by wt (1. 2:1 w/w, H//2O vertical DNA), the in-pulse luminescence spectrum is similar to that of dry DNA. These finding are discussed in terms of energy or charge migration induced in DNA upon irradiation and the possible effects of conformational charges, caused by hydration, on charge migration.