Study On The Interaction Of Tribromomethane And Metal Ions With DNA And Proteins

Chlorinated drinking water contains a number of different by-products formed during the chlorination process from organic matter. In this paper, the interaction between tribromomethane(CHBr₃)and DNA has been investigated by using absorption spectroscopy , and the interaction between CHBr₃ and bovine serum albumin(BSA), hemoglobin(Hb) and Tryptophan (Trp) were studied by using fluorescence spectroscopy. The experimental results indicated that CHBr₃ have strongly binding capacity with DNA (the binding constant K=4242L·mol^-1) and have two binding sites, DNA mightbe coordinate with the base groups of DNA. The fluorescence quenching of BSA and Hb induced by CHBr₃ follows a static quenching procedure. The binding constant between BSA and CHBr₃ is greater than that between Hb and CHBr₃, possibly caused by the differences of the structure of the proteins.To better understand the influences of the metal ion(Cd²⁺)existed in body or in drinking water, this article also studied the interaction between Cd²⁺ ion and DNA, BSA, Hb. The results showed that Cd²⁺ ion have weak binding capacity with DNA and the different combination mode with DNA; the phosphate groups is a possible binding site of Cd²⁺ ion to DNA. The fluorescence quenching of BSA induced by Cd²⁺ ion follow static quenching procedure; On the contrary, the fluorescence emission of Hb was enhanced when Cd²⁺ ion was added. Thus the combination mechanism is different.The ternary interactions of CHBr₃-DNA-Cd²⁺ and CHBr₃-proteins-Cd²⁺ were also determined in this article. Results showed that Cd²⁺ ion could slightly enhanced the binding constant of CHBr₃ to DNA and strengthen the binding capacity of CHBr₃ to DNA. When there were CHBr₃ and Cd ion in body, Cd²⁺ ion maybe strengthen the toxic effect of CHBr₃. Metal ions Cd²⁺ could increase the binding constants of CHBr₃ to BSA and Hb, the possible cause is Cd²⁺ maybe change the conformation of proteins, make CHBr₃ easily combine to proteins so that influent the biological functions of BSA and Hb.