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Fluorescence emission and enhanced photochemical stability of ZnII-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate interacting with native DNA

  • Autori: Barone, G.; Ruggirello, A.; Silvestri, A.; Terenzi, A.; TURCO LIVERI, V.
  • Anno di pubblicazione: 2010
  • Tipologia: Articolo in rivista (Articolo in rivista)
  • Parole Chiave: DNA; Fluorescence spectroscopy; Intercalation; Photooxidation; Schiff bases; Zinc
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The photophysical and photochemical properties of the cationic ZnII complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL2+) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL2+ is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL2+, both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL2+ undergoes a photoinduced two-electron oxidation process. According to this picture, the protective action of DNA toward the intercalated ZnL2+ was attributed to an effective inhibition of the ZnL2+ photooxidation. In this context, it can be considered that DNA-intercalated ZnL2+ is located in a region more hydrophobic than that sensed in the bulk water solvent. Moreover, by a thorough analysis of steady state and time-resolved fluorescence spectra, the interaction process can be consistently explained in terms of a complete intercalation of the complex molecules and that the polarity of the environment sensed by intercalated ZnL2+ is comprised between that of methanol and ethanol.