Ultraviolet irradiation of nucleic acids complexes with heavy atoms

Abstract— We have studied the luminescence (at 77°K) and photochemistry (at 298°K) of a variety of polynucleotides complexed with Ag + . In all cases we observed that Ag + induces a 'heavy atom effect' as indicated by quenching of fluorescence, enhancement of phosphorescence, and reduction of triplet lifetimes. The enhancement by Ag + of the phosphorescence intensity of poly (dT) and DNA paralleled a 20‐fold enhancement of the rate of thymine dimerization. These results suggest a possible triplet precursor for thymine dimerization in Ag + complexes. Dimers were also made with a variety of triplet sensitizers, and Ag + increased the dimer yield two‐ to four‐fold, depending on the sensitizer used.