The Interaction Of Amion Acid Schiff Base And Its Complexes With DNA

In this paper, a Schiff base containing an azomethine group is prepared by the condensation of vanillin with L-Tryptophan, and its complexes of Sm(Ⅲ), Eu(Ⅲ), Mg(Ⅱ), Ni(Ⅱ), Zn(Ⅱ) were also synthesized. The Shiffe base and its complexes were characterized by IR spectroscopy, ultraviolet spectroscopy, fluorescence spectroscopy, etc. Then the interaction of the Schiff base and its complexes with DNA has been investigated systematically by spectroscopy, viscosity approaches and cyclic voltammetry. Their combine ratios, combine constants and thermodynamic functions were calculated.The binding ratios between K[HL],Sm(Ⅲ)L,Eu(Ⅲ)L,Mg(Ⅱ)L,Ni(Ⅱ)L,Zn(Ⅱ)L and DNA in physiological pH environment (pH=7.40) were determined as 5:1, and the apparent molar absorptivities were confirmed by molar ratio method. The binding constants are K_B^θ28°C K[HL] =1.94×10⁵ L·mol^-1, K_B^θ25°C Sm(Ⅲ)L=1.19×10⁵ L·mol^-1, K_B^θ22°C Eu(Ⅲ)L =2.29×10⁵ L·mol^-1, K_B^θ13°C Mg(Ⅱ)L=4.32×10⁴ L·mol^-1, K_B^θ13°C Ni(Ⅱ)L=9.90×10⁴ L·mol^-1, K_B^θ13°C Zn(Ⅱ)L =1.43×10⁴ L·mol^-1 , respectively.. Combined with fluorimeteric studies, scatchard methods, CD spectroscopy, cyclic voltammetry and viscosity methods, the results suggest that the interaction modes between K[HL], Sm(Ⅲ)L and DNA are mainly with intercalation and groove binding , the interaction modes between Eu(Ⅲ)L, Mg(Ⅱ)L, Ni(Ⅱ)L, Zn(Ⅱ)L and DNA are mainly with intercalation and involving some electrostatic interaction.The molecular structure of L-tryptophan containing aromatic fused ring indole plane, which may be the internal structure reasons of the Shiffe base and its complexes can insert to DNA molecule.