Spectroscopic studies on the interaction of Safranine T with DNA in β-cyclodextrin and carboxymethyl-β-cyclodextrin

The interaction of Safranine T (ST) with cyclodextrins (CDs) including β-cyclodextrin (β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD) and DNA in aqueous solution is studied by UV-vis absorption and steady-state fluorescence technique. The interactive model of ST with double stranded DNA has been investigated by means of the inclusive action of β-CD and CM-β-CD. Based on the changes of absorption, fluorescence and resonance light scattering (RLS) spectra, the intrinsic binding constant (Kap) and the binding site number (n) of ST with DNA and the inclusion complexes ST-CD with DNA are obtained in the case of 20 mmol/L Tris-HCl buffer solution (pH 7.2). According to the experimental results, it can be inferred that the interactive model of dimer ST with DNA is “electrostatic binding”, while the monomer ST with DNA is “intercalative binding”.