Nucleic acid hydrolysis complexes

RNA hydrolysis, 45 285-287, 297-299 metalloenzymes, 45 251-252 bleomycin, 45 252-260, 299 nucleic acid hydrolysis metal ions and, 45 283-285 by oligonucleotide modified with metal complexes, 45 297-299 of phosphodiesters, 45 251, 287-297 by ribozymes, 45 285-287 cleavage by iron bleomycin, 43 140 polymerase, arsonomethyl phosphonate analogue, 44 201-202 substructures, 43 133-134 transfer... 

Chromium, Manganese, Cobalt, Nickel, Ruthenium, Rhodium, Platinum, and Uranium Complexes Metalloporphsrrin Complexes Metal Ions and Nucleic Acid Hydrolysis... 

In the past, dissociation of the nucleoprotein complex has been brought about by salt solutions or by heat denaturation,129 but, more recently, decomposition has been effected by hydrolysis with trypsin,126 or by the use of dodecyl sodium sulfate130 or strontium nitrate.131 Some virus nucleoproteins are decomposed by ethyl alcohol.132 This effect may be similar to that of alcohol on the ribonucleoproteins of mammalian tissues. If minced liver is denatured with alcohol, and the dried tissue powder is extracted with 10% sodium chloride, the ribonucleoproteins are decomposed to give a soluble sodium ribonucleate while the deoxyribonucleoproteins are unaffected.133 On the other hand, extraction with 10 % sodium chloride is not satisfactory unless the proteins have first been denatured with alcohol. Denaturation also serves to inactivate enzymes of the tissues which might otherwise bring about degradation of the nucleic acid during extraction. 

Macromolecules such as proteins, polysaccharides, nucleic acids differ only in their physicochemical properties within the individual groups and their isolation on the basis of these differences is therefore difficult and time consuming. Considerable decreases may occur during their isolation procedure due to denaturation, cleavage, enz3rmatic hydrolysis, etc. The ability to bind other molecules reversibly is one of the most important properties of these molecules. The formation of specific and reversible complexes of biological macromolecules can serve as basis of their separation, purification and analysis by the affinity chromatography [6]. 

The protein portion of the nucleoproteins is basic in nature and being complex in structure may form several types of linkage, depending upon the type of nucleic acid. In gastric digestion or hydrolysis with weak acid, nucleoproteins yield protein and nuclein. The latter in pancreatic digestion or hydrolysis with weak alkali yields additional protein and nucleic add. See also Nucleic Acids. 

Oxidative phosphorylation is central to the metabolism of all higher organisms, because the free energy of hydrolysis of the ATP so generated is used in the synthesis of, inter alia, nucleic acids (Chaps. 7 and 16), proteins (Chaps. 4,9, and 17), and complex lipids (Chap. 6), as well as in processes as diverse as muscle contraction (Chap. 5) and the transmission of nerve impulses. 

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. 

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. 

Sephadex has been used to a lesser extent in the nucleic acid field. - The G-50 type will separate RNA of high molecular weight from nucleosides or bases. However, Sephadex does not separate the complex mixture of mono- to hexanucleotides obtained by enzymic hydrolysis of RNA. Sephadex-25 has been used as the supporting medium for partition chromatography of yeast-soluble RNA. ... 

The reactions of transition-metal complexes with polynucleotides generally fall into two categories (i) those involving a redox reaction of the metal complex that mediates oxidation of the nucleic acid and (ii) those involving coordination of the metal center to the sugar-phosphate backbone so as to mediate hydrolysis of the polymer. Both redox and hydrolytic reactions of metal complexes with nucleic acids have been exploited with much success in the development of tools for molecular biology. 

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