FEMTOSECOND DEACTIVATION OF THIONINE SINGLET-STATES BY MONONUCLEOTIDES AND POLYNUCLEOTIDES

The sub-picosecond deactivation of the thionine singlet state by guanine-containing polynucleotides or mononucleotides has been measured by femtosecond transient absorption spectroscopy. The thionine singlet state was also quenched, although less efficiently, by adenine nucleotides. In contrast, the lifetime of the methylene blue singlet state is only slightly affected by adenine-containing species, although it was rapidly quenched by guanine. A strong correlation was observed between the rates of singlet state deactivation and the DELTAG-degrees values for electron transfer in the dye/nucleotide base systems, although with the thionine/guanine systems no electron transfer products were detected.