四种金属离子对CHBr_3和小牛胸腺DNA间结合作用的影响

The effect of Cu^(2+),Co^(2+),Cd^(2+) and Mg^(2+) on the interactions between bromoform and calf thymus DNA

采用紫外光谱和荧光光谱法研究了CHBr3与离体小牛胸腺DNA(ctDNA)间的相互作用,以及Cu2+、Co2+、Cd2+、Mg2+4种金属离子单独或共存时对CHBr3与ctDNA结合的影响.结果表明:4种金属离子与CHBr3、ctDNA均能发生基态络合反应,络合物的生成导致体系的紫外吸收峰强度和形状改变,使ctDNA-溴化乙锭体系的荧光发生了不同程度的猝灭;向CHBr3-ctDNA-溴化乙锭体系中分别或同时加入4种金属离子后,Cu2+、Co2+、Cd2+可减弱两者之间的结合,减弱顺序为Cu2+>Co2+>Cd2+,Mg2+可加强两者之间的结合,4种金属离子同时加入后出现不同于4种金属离子单独加入时的中间类型.据此推断,CHBr3可能主要是通过嵌插作用与ctDNA碱基结合,金属离子对CHBr3与ctDNA结合的影响主要取决于金属离子与DNA的碱基和磷酸基团间结合的相对亲和比.

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 Cu^2＋,Co^2＋,Cd^2＋ 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 Cu^2＋,Co^2＋,Cd^2＋ （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.