DNA-metal ion complex

The importance of coordination in the biochemistry of essential metallic elements may be illustrated by numerous examples of metal complexes of which the following are representative the iron complex hemoglobin and numerous enzymes containing the heme and related structures such as catalases, peroxidases and cytochromes and the iron-containing proteins ferritin, transferrin, and hemosiderin the zinc complexes zinc-insulin, carbonic anhydrase and the carboxypeptidases the cobalt complex vitamin B12 the copper complex, ceruloplasmin the molybdenum-containing enzymes, xanthine oxidase, and nitrate reductase DNA-metal ion complexes. 

The environmentally important heavy metal Cd was undetectable in this assay, as were Mo and Rb, despite the fact that all cationic metal ions are known to interact with nucleic acids. Why then does this assay detect only a discrete subset of these interactions The simplest explanation is that only specific structural changes in the DNA helix effect the affinity of the dye. Attempts to compare our results with the vast literature in this area has been complicated by the fact that the experiments are rarely carried out under the same conditions. We and others have shown that the stability of DNA metal ion complexes are extremely sensitive to minor changes in the assay condition, as well as contaminants which further complicates comparative analysis. 

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