Effects of chelating agents EDTA, phytin and deferoxamine on the heavy metal complexes of DNA

Department of Biochemistry & Biophysics, Kalyani University, Kalyani-741 235, India

Manuscript received 13 August 1997, revised 18 May 1998, accepted 19 May 1998

The characteristic CD spectrum of B-conformation of DNA is highly perturbed by Ag⁺ and Hg²⁺ but not by Cu²⁺, Zn²⁺, Mn²⁺ etc. This perturbation is due to the formation of coordination complexes with the DNA bases within the helix by the former two metals. While the chelating agents deferoxamine and EDTA partially reverse the perturbed CD spectrum of DNA-Ag⁺, phytin prac­tically has no effect. But phytin as well as deferoxamine and EDTA effectively but partially reverse the CD spectrum of DNA-Hg²⁺ to that of free DNA. The DNA-Hg²⁺ complex seems to be weaker than DNA-Ag⁺. Thus the iron chelating drug deferoxamine has an additional beneficial effect of partially nullifying mercury and silver poisoning; phytin is weakly effective in case of mercury poisoning. EDTA is more effective in silver as well as mercury poisoning compared to the other two chelating agents.