The Interaction Of Rare Earth Complexes Of Riboflavin, Methylene Blue And Fluorescein With Herring Sperm DNA

In this work, ultraviolet spectroscopy, fluorescence spectroscopy, circular dichroism method, viscosity method and thermodynamic method were used to study interaction mode between the different systems of rare earth complexes of riboflavin, methylene blue and fluorescein with herring sperm DNA. Their combine ratios, combine constants and thermodynamic functions were calculated. The binding ratios between Dy(Ⅲ)-RF, Sm(Ⅲ)-RF, Sm(Ⅲ)-MB, Dy(Ⅲ)-MB, Sm(Ⅲ)-FSC and DNA in physiological pH environment (pH7.40) were determined as nDy(Ⅲ)(RF)3:nDNA=5:1, nSm(Ⅲ)(RF)3:nDNA=5:1, nSm(Ⅲ)(MB)3:nDNA=5:1, nDy(Ⅲ)(MB)3: nDNA=8:1, nSm(Ⅲ)(FSC) 3:nDNA=5:1, nDym(Ⅲ)(FSC) 3:nDNA=5:1, and the apparent molar absorptivities were confirmed by molar ratio method. The binding constants at 37℃are K_B~θDy(Ⅲ)(RF)3-DNA=4.78×10~5L/mol, K_B~θSm(Ⅲ)(RF)3-DNA=4.73×10~8L/mol, K_B~θSm(Ⅲ)(MB)3-DNA=1.25×10~5L/mol, K_B~θDy(Ⅲ)(MB)3-DNA=6.74×10~5L/mol, K_B~θSm(Ⅲ)(FSC)3-DNA=1.88×10~5 L/mol, K_B~θDy(Ⅲ)(FSC)3-DNA=2.45×10~4 L/mol. Thermodynamic function computation demonstrates thatΔrSm? is the primary driving power of the interaction between Dy(Ⅲ)(RF)3, Sm(Ⅲ)(RF)3, Dy(Ⅲ)(MB)3, Sm(Ⅲ)(MB)3, Dy(Ⅲ)(FSC)3 and DNA, butΔrHm? is the primary driving power of the interaction between Sm(Ⅲ)(FSC)3 and DNA. By combination analysis of the Scatchard method, Circular dichroism spectrometry and Viscosity method, we suggested that the interaction mode between Sm(Ⅲ)(RF)3, Dy(Ⅲ)(RF)3 complexes and herring sperm DNA are groove and electrostatic binding, and Dy(Ⅲ)MB)3, Sm(Ⅲ)(MB)3 complexes and herring sperm DNA are electrostatic and intercalation binding, Sm(Ⅲ)(FSC)3 complexe and Dy(Ⅲ)(FSC)3 complexe and herring sperm DNA are groove and intercalation bindings.