Nucleic acids metal coordination

Nucleic Acid Metal Ion Interactions Nutritional Aspects of Metals Trace Elements Peptide-Metal Interactions Zinc Enzymes Zinc Inorganic Coordination Chemistry. 

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. 

Technetium-99m coordination compounds are used very widely as noniavasive imaging tools (35) (see Imaging technology Radioactive tracers). Different coordination species concentrate ia different organs. Several of the [Tc O(chelate)2] types have been used. In fact, the large majority of nuclear medicine scans ia the United States are of technetium-99m complexes. Moreover, chiral transition-metal complexes have been used to probe nucleic acid stmcture (see Nucleic acids). For example, the two chiral isomers of tris(1,10-phenanthroline)mthenium (IT) [24162-09-2] (14) iateract differentiy with DNA. These compounds are enantioselective and provide an addition tool for DNA stmctural iaterpretation (36). 

It is well known that a great variety of biomolecules exist where metals and metalloids are bound to proteins and peptides, coordinated by nucleic acids or complexed by polysaccharides and small organic ligands such as organic acids.55 Most proteins contain amino acids with covalently bonded heteroelements such as sulphur, selenium, phosphorus or iodine.51 Several reviews have been published on the development of mass spectrometric techniques for bioanalysis in metal-lomics , which integrate work on metalloproteins, metalloenzymes and other metal containing biomolecules.1 51 53 54 56-59 The authors consider trace metals, metalloids, P and S (so-called... 

Nucleic acids - [NUCLEIC ACIDS] (Vol 17) -in cell culture products [CELL CULTURE TECHNOLOGY] (Vol 5) -coordination compounds as probes [COORDINATION COMPOUNDS] (Vol 7) -electrophoresis of [ELECTROSEPARATIONS - ELECTROPHORESIS] (Vol 9) -phosphorus m [MINERALNUTRIENTS] (Vol 16) -role m sterilization [DISINFECTANTS AND ANTISEPTICS] (Vol 8) -ruthenium cmpds as probes [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19)... 

The biological functions of the nucleic acids involve the participation of metal ions. In particular K+ and Mgr+ stabilize the active nucleic acid conformations. Mg2+ also activates enzymes which are involved in phosphate transfer reactions and in nucleotide transfer. The monomeric nucleotides are also involved in a number of metabolic processes and here again metal ions are implicated. Consequently, there has been considerable attention focussed on the coordination properties of these molecules as a means of understanding the mechanism of the metal ion involvements. A number of reviews are available which cover the studies on metal interactions.113 117... 

One may draw an analogy between nucleic acids and helicates, with on one side the polynucleotide strands and their interaction through hydrogen bonding and on the other side the oligobipyridine strands and their binding together via metal ion coordination. 

Study of the metal coordination environment in metalloproteins, nucleic acids, carbohydrates, membranes... 

X-ray and neutron diffraction patterns can be detected when a wave is scattered by a periodic structure of atoms in an ordered array such as a crystal or a fiber. The diffraction patterns can be interpreted directly to give information about the size of the unit cell, information about the symmetry of the molecule, and, in the case of fibers, information about periodicity. The determination of the complete structure of a molecule requires the phase information as well as the intensity and frequency information. The phase can be determined using the method of multiple isomor-phous replacement where heavy metals or groups containing heavy element are incorporated into the diffracting crystals. The final coordinates of biomacromolecules are then deduced using knowledge about the primary structure and are refined by processes that include comparisons of calculated and observed diffraction patterns. Three-dimensional structures of proteins and their complexes (Blundell and Johnson, 1976), nucleic acids, and viruses have been determined by X-ray and neutron diffractions. 

The larger biomolecules that have potential Al3+ binding sites are phosphate-bearing biomolecules such as ATP, membrane phospholipids and nucleic acids. It is important to recognize that the metal coordination of these biomolecules might lead to serious disgorges in central biological processes necessary to cell homeostasis and consequently for its overall healthy condition [21]. 

Hydrolytic catalysis by metal ions is also important in the hydrolysis of nucleic acids, especially RNA (36). Molecules of RNA that catalyze hydrolytic reactions, termed ribozymes, require divalent metal ions to effect hydrolysis efficiently. Thus, all ribozymes are metalloenzymes (6). There is speculation that ribozymes may have been the first enzymes to evolve (37), so the very first enzymes may have been metalloenzymes Recently, substitution of sulfur for the 3 -oxygen atom in a substrate of the tetrahymena ribozyme has been shown to give a 1000-fold reduction in rate of hydrolysis with Mg2+ but no attenuation of the hydrolysis rate with Mn2+ and Zn2+ (38). Because Mn2+ and Zn2+ have stronger affinities for sulfur than Mg2+ has, this feature provides strong evidence for a true catalytic role of the divalent cation in the hydrolytic mechanism, involving coordination of the metal to the 3 -oxygen atom. Other examples of metal-ion catalyzed hydrolysis of RNA involve lanthanide complexes, which are discussed in this volume. 

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