Synthesis and DNA interaction of a Sm(III) complex of a Schiff base derived from vanillin and L-tryptophan

Abstract

The interaction between the Sm(III) complex of an ionic Schiff base [HL]^-, derived from vanillin and L-tryptophan, and herring sperm DNA at physiological pH (7.40) has been studied by UV-Vis absorption, fluorescence and viscosity methods. The binding ratios n_Sm(III) : n_K[HL] = 1:1 and n_Sm(III)L: n_DNA = 5:1 were confirmed by a mole ratio method. The calculated binding constants of [Sm(III)L]⁺ with DNA at 25 and 37 ^oC were 1.19 × 10⁵ M^-1 and 3.96 × 10⁴ M^-1, respectively. The thermodynamic parameters demonstrate that the interaction between [Sm(III)L]⁺ and DNA is driven mainly by enthalpy. Fluorimetric studies show that [Sm(III)L]⁺ is able to displace intercalated acridine orange. Combined with Scatchard methods, circular dichroism spectroscopy and viscosity measurements, the results indicate that the interaction between [Sm(III)L]⁺ and herring sperm DNA is mainly by intercalation with some groove binding.

KEY WORDS: Vanillin, L-Tryptophan, Sm(III) complex of Schiff base, Herring sperm DNA, Interaction

Bull. Chem. Soc. Ethiop. 2011, 25(2), 197-207.