[Study on the fluorescence characteristics of the interaction between DNA and two halogenated fluoresceins]

The fluorescence characteristics of the interaction between DNA and two halogen fluoresceins, tetrabromofluorescein (TBF) and tetrachlorotetrabromofluorescein (TTF), were studied. The result showed that for TBF, lamda ex/ lamda em were 518 nm/540 nm, and for TTF, they were 540 nm/560 nm. The intensity of fluorescence of TBF and TTF changed in the presence of DNA. The fluorescence quenching studies indicated that TBF binds to DNA in the groove and the polarization experiments showed that TBF is intercalated into the DNA base pairs. So the comprehensive interaction mode of TBF with DNA may be that TTF is intercalated into DNA base pairs and binds to DNA in the groove. Both the fluorescence quenching studies and the polarization experiments indicated that TTF is intercalated into the DNA base pairs. It was also found that ionic strength could affect the interaction of TBF/TTF and DNA. The binding constants K are 1 x 10(6) L x mol(-1) and 2 x 10(6) L x mol(-1), and the binding site numbers n are 0.62 and 0.16 for TBF and TTF, respectively.