Interaction mode between methylene blue-Sm(III) complex and herring sperm DNA

Abstract

Spectroscopic and viscosity methods were applied to investigate the interaction between methylene blue (MB)-Sm(III) complex and herring sperm DNA by using acridine orange as a spectral probe in Tris-HCl buffer (pH 7.40). By means of molar ratio method, the binding ratios between MB-Sm(III) and DNA were determined as n_Sm(III):n_MB =1:3, n_{MB-Sm(III) complex}:n _DNA = 8:1, and the apparent molar absorption coefficient of ε_{MB-Sm(III)-DNA} was found to be 7.01×10⁵ M^-1·cm^-1. The bonding constants at different temperatures K^θ_292K = 7.35×10⁵ M^-1, K^θ_310K = 1.25×10⁵ M^-1 were obtained by double reciprocal method. Thermodynamic function computation demonstrates that Δ_rS_m^Ө is the primary driving power of the interaction between MB-Sm(III) and herring sperm DNA. By combination analysis of the Scatchard method, circular dichroism spectroscopy and viscosity method, it suggests that the interaction mode between MB-Sm(III) complex and herring sperm DNA are a mixed binding, which contains partial intercalation and electrostatic interaction.

KEY WORDS: Methylene blue-Sm(III), Complex, Herring sperm DNA, Interaction

Bull. Chem. Soc. Ethiop. 2012, 26(3), 395-405.

DOI: http://dx.doi.org/10.4314/bcse.v26i3.8