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- 저자 : Caronna, Tullio (검색결과 1 건)
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Passeri, Rosita,Aloisi, Gian Gaetano,Elisei, Fausto,Latterini, Loredana,Caronna, Tullio,Fontana, Francesca,Sora, Isabella Natali Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.11
In this work, three compounds having the same organic moiety (N-methyl-5-azahelicenium salts) but different counterions ($I^-$, $NO_3{^-}$ and $COOCF_3{^-}$) have been investigated in buffered aqueous solutions and in the presence of DNA to give information on the counterion effects on the binding. In particular, the absorption spectra, fluorescence quantum yields and fluorescence lifetimes in aqueous solution for free organic molecules have been determined by steady-state and time-resolved spectrofluorimetric measurements. The obtained values are compared with those of the chromophores in the presence of increasing concentrations of DNA. The results allow determination of the association constants ($K_a$) and the number of base couples per chromophore molecule (n) by means of the McGhee Von Hippel model. The binding parameters are strongly affected by the nature of counterions since the highest $K_a$ value was determined for the compound having $COOCF_3{^-}$; on the other hand the $NO_3{^-}$ derivative is able to interact with the highest number of binding sites. The morphology and structural properties of the DNA-chromophore complexes were investigated by circular dichroism (CD) and atomic force microscopy (AFM). The data revealed that $I^-$ and $COOCF_3{^-}$ derivatives preferentially form intercalation complexes, while the $NO_3{^-}$ salt is able to form intercalation and grove binding complexes at the same time.
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