Transition metals nucleic acid-metal interactions

The first chapter will start with a discussion of the methods being employed to elucidate the chemical and structural possibilities of metal nucleic acid interactions. This will be followed by specific reactions of some transition elements with the free bases, the nucleosides, the nucleotides and finally the polymer nucleotides. 

The knowledge of the chemistry and structure of nucleic acids as well as their metabolic and catabolic pathways has been extensively increased. However, there is very little evidence about the role of transition elements in the biochemistry of nucleic acids. Therefore, this review should emphasize the present status of the literature about studies of transition metal interactions with the monomer and polymer units of nucleic acids. Although this survey is far from being comprehensive it is hoped that the data collected here will be helpful for further investigations on the biochemical behavior of transition metals in nucleic acid metabolism. 

This method is especially suitable for studies with polymer nucleotide-metal ion interaction. When dissolved nucleic acids are exposed with and without metal ions to an increase of temperature structural changes, some reversible, some irreversible can be observed (27, 24, 27, 30, 39, 54—56, 75, 100, 108). The two parameters Tm (or midpoint of the transition) and a (the width of the transition) allow conclusions about conformational alterations. The application of this procedure for quantitative studies of metal complexing still needs to be elucidated. 

In the previous chapters the reactivity of metal ions with the monomer units of nucleic acids has been discussed. This section will deal with the binding of transition metals to the polynucleotides. There are also three types of complexes to be expected the metal-ring, the intermediate and the metal chain complex. The effect of the ribose or deoxyribose residue on the stability constants can be neglected since the reactivity of these sugars with cations is extremely low. However, as it will be seen later, the hydrolysis of polyribonucleotides is markedly facilitated by interaction of metal ions with the 2 —OH groups of the ribose. 

Carbene Complexes Carbonyl Complexes ofthe Transition Metals Cyanide Complexes of the Transition Metals Dinuclear Organometallic Cluster Complexes Electron Transfer in Coordination Compounds Electron Transfer Reactions Theory Electronic Structure of Organometallic Compounds Luminescence Nucleic Acid-Metal Ion Interactions Photochemistry of Transition Metal Complexes Photochemistry of Transition Metal Complexes Theory Polynuclear Organometallic Cluster Complexes. 

The coordination properties of the nucleobases have been reviewed by Houlton (40) and by Lippert (2). In a recent review, Lippert discussed the influence of the metal coordination on the piSTa of the nucleobases (41), which correlates with their coordination properties. While the coordination properties of nucleobases, nucleosides, and nucleotides have been extensively studied and reviewed, the number of articles dedicated to the coordination properties of nucleic acids is signihcantly smaller. DeRose et al. (42) recently published a systematic review of the site-specific interactions between both main group and transition metal ions with a broad range of nucleic acids from 10 bp DNA duplexes to 300 00 nucleotide RNA molecules as well as with some nucleobases, nucleosides, and nucleotides. They focused on results obtained primarily from X-ray crystallographic studies. Egli also presented information on the metal ion coordination to DNA in reviews dedicated to X-ray studies of nucleic acids (43, 44). Sletten and Fr0ystein (45) reviewed NMR studies of the interaction between nucleic acids and several late transition metal ions and Zn. Binding of metal complexes to DNA by n interactions has been reviewed by Dupureur and Barton (46). 

This chapter presented the results of research aimed at the combined use of transition metal coordination and nucleic acid hybridization to construct hybrid inorganic-nucleic acid supramolecular structures. The interaction of alkali metal ions with DNA and RNA is nonspecific, and has been long... 

In this chapter we first summarize the basics needed to consider the interactions of metal ions and complexes with nucleic acids. What are the structures of nucleic acids What is the basic repertoire of modes of association and chemical reactions that occur between coordination complexes and polynucleotides We then consider in some detail the interaction of a simple family of coordination complexes, the tris(phenanthroline) metal complexes, with DNA and RNA to illustrate the techniques, questions, and applications of metal/nucleic-acid chemistry that are currently being explored. In this section, the focus on tris(phenanthroline) complexes serves as a springboard to compare and contrast studies of other, more intricately designed transition-metal complexes (in the next section) with nucleic acids. Last we consider how Nature uses metal ions and complexes in carrying out nucleic-acid chemistry. Here the principles, techniques, and fundamental coordination chemistry of metals with nucleic acids provide the foundation for our current understanding of how these fascinating and complex bioinorganic systems may function. 

Now we may examine in detail the interaction of one class of metal complexes with nucleic acids, how these complexes bind to polynucleotides, the techniques used to explore these binding interactions, and various applications of the complexes to probe biological structure and function. Tris(phenanthroline) metal complexes represent quite simple, well-defined examples of coordination complexes that associate with nucleic acids. Their examination should offer a useful illustration of the range of binding modes, reactivity, techniques for study, and applications that are currently being exploited and explored. In addition, we may contrast these interactions with those of other transition-metal complexes, both derivatives of the tris(phenanthroline) family and also some complexes that differ substantially in structure or reactivity. 

Many of the same techniques employed in studying the basic chemistry of coordination complexes can be be used in following the binding of transition-metal complexes to nucleic acids, but biochemical methods, with their often exquisite sensitivity, become valuable aids as well in delineating specific binding interactions. Tris(phenanthroline) metal complexes are particularly useful to illustrate this point, since here the metal center in the complex is selected in terms of the technique used for examination. 

A great diversity exists in the design of nucleic acid probes upon transition metal chemistry in part because of the abundance of different binding interactions to nucleic acids that may be exploited. Metal complexes bind to DNA through both covalent and noncovalent modes as illustrated in Fig. 2. 

The recognition and sensing of nucleic acids is another area of research that has grown rapidly in recent times. Many snch systems are based on the use of transition metal complexes, owing to their strong electrostatic interactions with the backbone of DNA and because they can additionally intercalate into DNA several examples of nonmetal-based intercalators (all organic) have been developed recently and show an excellent selectivity and... 

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