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

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 he lix by the former two metals. While the chelating agents deferoxamine and E DTA partially reverse the perturbed CD spectrum of DNA-Ag+, phytin practica lly 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 d rug deferoxamine has an additional beneficial effect of partially nullifyin g mercury and silver poisoning; phytin is weakly effective in case of mercu ry poisoning. EDTA is more effective in silver as well as mercury poisoning compared to the other two chelating agents.