Copper polynucleotides

Polymers are ubiquitous. Natural polymers such as proteins (polyamino acids), DNA (polynucleotides), and cellulose (polyglucose) are the basic building blocks of plant and animal life. Synthetic organic polymers, or plastics, are now among our most common structural materials. In the United States we make and use more synthetic polymers than we do steel, aluminum, and copper combined—in 1984, 46 billion pounds, worth 18 billion dollars. 

The diversity of structures is matched by a wide range of mechanisms. While the ruthenium—amines may act by a DNA-binding mechanism the rhodium carboxylates inhibit DNA synthesis but do not bind directly to the doubly stranded polynucleotide. In the latter case a possible mechanism is inhibition of precursor enzymes. Copper thiosemicarbazones and gold diphosphines appear to act by release of the toxic ligand. For thiosemicarbazones the ultimate target is ribonucleotide reductase. Other copper complexes have been developed to mimic the action of superoxide dismutase. 

In contrast to Mg + and Mn +, which stabilize secondary structures in DNA and RNA, Cu + destabilizes DNA and RNA double helices, and this is attributed to the ability of copper to bind to the nucleic acid bases. Chao and Kearns have recently explored the possibility that this binding, as detected by electron and nuclear magnetic resonance spectroscopy, might be used to probe certain structural features of nucleic acid molecules, such as the looped out regions of tRNAs. The nature of the Cu complexes formed with nucleosides and nucleotides varies with the specific nucleic acid derivatives used and also the pH. Thus, in the pH range 8.5—10.0, copper forms a water-soluble complex with the ribose OH groups of the ribonu-cleosides and 5 -ribonucleotides, but these complexes cannot form with any of the deoxynucleosides or the 2 - and 3 -ribonucleotides. It is suggested that copper(ii) could stabilize unusual polynucleotide structures or interactions in certain enzymatic systems the latter could, for example, be responsible for translational errors in the RNA,DNA polymerase system which are known to be induced by transition metals. 

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