INTERACTION MODE BETWEEN METHYLENE BLUE-Sm(III) COMPLEX AND HERRING SPERM DNA

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 epsilon(MB-Sm(III)-DNA) was found to be 7.01x10(5) M-1.cm(-1). The bonding constants at different temperatures K-292K(0) = 7.35x10(5) M-1, K-310K(0) = 1.25x10(5) M-1 were obtained by double reciprocal method. Thermodynamic function computation demonstrates that Delta rSm(circle minus) 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