Interaction between tryptophan-Sm(III) complex and DNA with the use of a acridine orange dye fluorophor probe

The interaction of the Trp-Sm(III) complex with herring sperm DNA (hs-DNA) was investigated with the use of acridine orange (AO) dye as a spectral probe for UV-vis spectrophotometry and fluorescence spectroscopy. The results showed that the both the Trp-Sm(III) complex and the AO molecule could intercalate into the double helix of the DNA. The Sm(III)-(Trp)3 complex was stabilized by intercalation into the DNA with binding constants: K(Ө)25°C  = 7.14 × 10(5)  L·mol(-1) and K(Ө) 37°C  = 5.28 × 10(4)  L·mol(-1), and it could displace the AO dye from the AO-DNA complex in a competitive reaction. Computation of the thermodynamic functions demonstrates that Δr Hm (Ө) is the primary driving power of the interaction between the Sm(III)(Trp)3 complex and the DNA. The results from Scatchard and viscometry methods suggested that the interaction mode between the Sm(III)(Trp)3 complex and the hs-DNA is groove binding and weak intercalation binding.