Nucleosides, RNA

In analogy with the designation of NRTIs and NNRTls for the nucleoside and nonnucleoside type of reverse transcriptase (RT) inhibitors to target HIV, the corresponding inhibitors to target HCV may be termed NRRIs (for nucleoside RNA replicase inhibitors) and NNRRIs (for nonnucleoside RNA replicase inhibitors). 

Base Abbre- viation RNA Nucleoside RNA Nucleotide DNA Nucleoside DNA Nucleotide... 

The most important derivatives of pyrimidines and purines are nucleosides Nucleosides are N glycosides m which a pyrimidine or purine nitrogen is bonded to the anomeric carbon of a carbohydrate The nucleosides listed m Table 28 2 are the mam building blocks of nucleic acids In RNA the carbohydrate component is d ribofuranose m DNA It IS 2 deoxy d ribofuranose... 

Nucleic Acids. Phosphoms is an essential component of nucleic acids, polymers consisting of chains of nucleosides, a sugar plus a nitrogenous base, and joined by phosphate groups (43,44). In ribonucleic acid (RNA), the sugar is D-ribose in deoxyribonucleic acids (DNA), the sugar is 2-deoxy-D-ribose. 

Antibiotic A201A. Antibiotic A201A (23), produced by S. capreolus is an /V -dimethyladenine nucleoside stmcturaHy similar to puromycin (19). Compound (23) which contains an aromatic acid and monosaccharide residues (1,4), inhibits the incorporation of amino acids into proteins but has no effect on RNA or DNA synthesis. Compound (23) does not accept polypeptides as does (19), and does appear to block formation of the initiation complex of the SOS subunit. It may block formation of a puromycin-reactive ribosome. 

Purine Nucleoside Derivatives. A number of purine nucleoside analogues are also found to be active against several DNA vimses (Fig. 3). The clinically active antiviral drug ara-A (9-P-D-arabinofuranosyladenine [5536-17-4] vidarabine, 23) is active against a number of DNA vimses in vivo and also inhibits certain RNA tumor vimses which repHcate through a DNA intermediate (43). Ara-A, was first synthesized in 1960 (44) and later... 

Nucleic acids are linear polymers of nucleotides linked 3 to 5 by phosphodi-ester bridges (Figure 11.17). They are formed as 5 -nucleoside monophosphates are successively added to the 3 -OH group of the preceding nucleotide, a process that gives the polymer a directional sense. Polymers of ribonucleotides are named ribonucleic acid, or RNA. Deoxyribonucleotide polymers are called deoxyribonucleic acid, or DNA. Because C-1 and C-4 in deoxyribonucleotides are involved in furanose ring formation and because there is no 2 -OH, only... 

FIGURE 11.29 The vicinal—OH groups of RNA are susceptible to nucleophilic attack leading to hydrolysis of the phosphodiester bond and fracture of the polynucleotide chain DNA lacks a 2 -OH vicinal to its 3 -0-phosphodiester backbone. Alkaline hydrolysis of RNA results in the formation of a mixture of 2 - and 3 -nucleoside monophosphates. 

DNA is not susceptible to alkaline hydrolysis. On the other hand, RNA is alkali labile and is readily hydrolyzed by dilute sodium hydroxide. Cleavage is random in RNA, and the ultimate products are a mixture of nucleoside 2 - and 3 -monophosphates. These products provide a clue to the reaction mechanism (Figure 11.29). Abstraction of the 2 -OH hydrogen by hydroxyl anion leaves a 2 -0 that carries out a nucleophilic attack on the phosphorus atom of the phosphate moiety, resulting in cleavage of the 5 -phosphodiester bond and formation of a cyclic 2, 3 -phosphate. This cyclic 2, 3 -phosphodiester is unstable and decomposes randomly to either a 2 - or 3 -phosphate ester. DNA has no 2 -OH therefore DNA is alkali stable. 

Genesis of nucleic bases, nucleotides, and nucleosides the problem of RNA origin and its role in life origin 99T3141. 

The nucleic acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are biological polymers that act as chemical carriers of an organism s genetic information. Enzyme-catalyzed hydrolysis of nucleic acids yields nucleotides, the monomer units from which RNA and DNA are constructed. Further enzyme-catalyzed hydrolysis of the nucleotides yields nucleosides plus phosphate. Nucleosides, in turn, consist of a purine or pyrimidine base linked to Cl of an aldopentose sugar—ribose in RNA and 2-deoxyribose in DNA. The nucleotides are joined by phosphate links between the 5 phosphate of one nucleotide and the 3 hydroxyl on the sugar of another nucleotide. 

These sorbents may be used either for selective fixation of biological molecules, which must be isolated and purified, or for selective retention of contaminants. Selective fixation of biopolymers may be easily attained by regulation of eluent polarity on the basis of reversed-phase chromatography methods. Effective isolation of different nucleic acids (RNA, DNA-plasmid) was carried out [115, 116]. Adsorption of nucleosides, nucleotides, tRN A and DNA was investigated. It was shown that nucleosides and nucleotides were reversibly adsorbed on... 

Attached by a covalent bond to carbon atom 1 of the deoxyribose ring is an amine (and therefore a base), which may be adenine, A (22) guanine, G (23) cytosine, C (24) or thymine, T (25). In RNA, uracil, U (26), replaces thymine. The base bonds to carbon atom 1 of deoxyribose through the nitrogen of the —NH— group (printed in red) and the compound so formed is called a nucleoside. All nucleosides have a similar structure, which we can summarize as the shape shown in (27) the lens-shaped object represents the attached amine. 

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