Study on the Interaction of Vitamin B 12 with DNA by Spectroscopy and Electrochemical Methods

The Interaction between vitamin B 12 (VB 12 ) and fish sperm DNA was investigated in physiological buffer (pH 7.4) using the methylene blue (MB) dye as a spectral probe by spetcrophotometery, viscosity measurements and cyclic voltammetry. The apparent binding constant of vitamin B 12 with DNA was found to be 3.2×10 5 mol −1 ·L. The voltammetric behavior of vitamin B 12 has been investigated at glassy carbon electrode using cyclic voltammetry. Thermodynamic parameters including Δ H 0 , Δ S 0 and Δ G 0 for the interaction between VB 12 and DNA have determined as −2.3×10 4 , 27.54 and −3.1×10 4 J·mol −1 ·K −1 respectively. One indication of DNA binding mode with VB 12 was the change in viscosity when a small molecule associates with DNA. The diffusion coefficients of VB 12 in the absence ( D 0 ) f and presence of DNA ( D 0 ) b was calculated as 5.04×10 −6 and 1.13×10 −6 cm 2 ·s −1 respectively. The results indicated that vitamin B 12 can bind to DNA and the major binding mode was intercalative binding.