The effect of Cu2+,Co2+,Cd2+ and Mg2+ on the interactions between bromoform and calf thymus DNA
四种金属离子对CHBr3和小牛胸腺DNA间结合作用的影响

Using the technique of ultraviolet absorption spectrometry and fluorescence spectrometry, this study examined the interactions between bromoform(CHBr3) and calf thymus DNA(ctDNA) with or without Cu2+, Co2+, Cd2+ and Mg2+individually or concurrently. The results show complex ground-state reactions among the metal ions, CHBr3and ctDNA, as evidenced by the variations in the peak of UV absorption intensity and shape in the ctDNA-ethidium bromide system. The interactions cause fluorescence quenching to various extents. The presence of Cu2+, Co2+, Cd2+ (ranked by decreasing strength) weakened the binding between CHBr3 and ctDNA, while Mg2+enhanced such binding. In addition, the simultaneous presence of the four metal ions resulted in intermediate impact, varying from the effect of the individual metal ions. The results suggest that CHBr3 is likely to intercalate into ctDNA and such intercalations mainly depend on the relative binding affinity of a metal ion to the bases and to the phosphate groups in DNA.