Phosphorescence of nucleic acids and DNA components at 77 K

Abstract

The emission spectra of nucleic acids, pyrimidine and purine nucleotides, nucleosides and bases and a series of pyrimidine derivatives were obtained using UV light excitation in glasses (ethanol and 2:1 mixtures of ethylene glycol and water (EGH 2O); also partly in butyronitrile and 2-methyltetrahydrofuran) at 77 K. The quantum yields of fluorescence Φ f and phosphorescence Φ p of some 30 compounds are presented; for several substituted uracils they are reported for the first time. The values cover a range from Φ f = 0.0002 and Φ p = 0.001 for uracil in ethanol to Φ f = 0.50 for guanosine in acidic ethanol and Φ p = 0.095 for guanosine-5′-monophosphate in EGH 2O (pH 6 – 7). The phosphorescence lifetime τ p at 77 K ranges from about 0.3 s (uracil moiety) to 3 s (adenine moiety). The measured τ p, Φ f and Φ p values are compared with those available in the literature.