Pyrimidine bases, ribonucleic acid

Pyrimidine natural products are particularly important (Scheme lb). The nucleic acids contain pyrimidine and purine bases ribonucleic acids (RNA) contain D-ribose and uracil, deoxyribonucleic acids (DNA) contain 2-deoxy-D-ribose and thymine and both types contain phosphate residues,... 

Nucleic acids are acidic substances present m the nuclei of cells and were known long before anyone suspected they were the primary substances involved m the storage transmission and processing of genetic information There are two kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Both are complicated biopolymers based on three structural units a carbohydrate a phosphate ester linkage between carbohydrates and a heterocyclic aromatic compound The heterocyclic aro matic compounds are referred to as purine and pyrimidine bases We 11 begin with them and follow the structural thread... 

As is well-known, nucleic acids consist of a polymeric chain of monotonously reiterating molecules of phosphoric acid and a sugar. In ribonucleic acid, the sugar component is represented by n-ribose, in deoxyribonucleic acid by D-2-deoxyribose. To this chain pyrimidine and purine derivatives are bound at the sugar moieties, these derivatives being conventionally, even if inaccurately, termed as pyrimidine and purine bases. The bases in question are uracil (in ribonucleic acids) or thymine (in deoxyribonucleic acids), cytosine, adenine, guanine, in some cases 5-methylcytosine and 5-hydroxymethylcyto-sine. In addition to these, a number of the so-called odd bases occurring in small amounts in some ribonucleic acid fractions have been isolated. 

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. 

Figure 35-6. A segment of a ribonucleic acid (RNA) molecule in which the purine and pyrimidine bases— guanine (G), cytosine (C), uracii (U), and adenine (A)—are held together by phosphodiester bonds between ribo-syl moieties attached to the nucieobases by N-giycosidic bonds. Note that the polymer has a polarity as indicated by the iabeied 3 -and 5 -attached phosphates.

In view of the difficulty of hydrolyzing the pyrimidine nucleosidic linkages, ribonucleic acids have been hydrolyzed to a mixture of purine bases and pyrimidine nucleotides which is then separated by paper chromatography.132, 163 164 This method has been employed extensively for the analysis of ribonucleic acids, and gives reproducible results,166 but it has not been used to any great extent for deoxyribonucleic acids, probably because, under these conditions of hydrolysis, they yield some pyrimidine deoxy-ribonucleoside diphosphates.166... 

Nitrogenous base plus sugar moiety are called nucleosides. Ribonucleic acids (RNA) resemble DNA in that nucleoside monophosphates are joined through phosphodiester bonds. RNAs differ in that the sugars are p-D-ribose units and the pyrimidine uracil is found in place of thymine. Molecular structures and nomenclature for nitrogenous bases, nucleosides, and nucleotides are delineated in Table 2.2. 

Ribonucleic Acid (RNA) Sugar is ribose, a phosphate group and a heterocyclic base. The base is either purine A or G and pyrimidine C or U. 

Nucleic Acid. A nucleic acid is a natural polynucleotide. It is a sugar-phosphate chain with purine and pyrimidine bases attached to it, as shown in Chart 10. If the sugar is deoxyribose and the pyrimidine bases are cytosine and thymine, the nucleic acid is deoxyribonucleic acid, DNA if the sugar is ribose, and the pyrimidine bases are (mostly) cytosine and uracil, the nucleic acid is ribonucleic acid, RNA. The sequence of bases may appear arbitrary and random, but it constitutes a meaningful code (see Code Word). In double-stranded nucleic acids,... 

The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are the chemical carriers of a cell s genetic information. Nucleic acids are biopolymers made of nucleotides joined together to form a long chain. These biopolymers are often found associated with proteins, and in this form they are called nucleoproteins. Each nucleotide comprises a nucleoside bonded to a phosphate group, and each nucleoside is composed of an aldopentose sugar, ribose or 2-deoxyribose, linked to a heterocyclic purine or pyrimidine base (see Section 4.7). 

The basic monomers of nucleic acids are nucleotides which are made up of heterocyclic nitrogen-containing compounds, purines and pyrimidines, linked to pentose sugars. There are two types of nucleic acids and these can be distinguished on the basis of the sugar moiety of the molecule, Ribonucleic acids (RNA) contain ribose, while deoxyribonucleic acid (DNA) contains deoxyribose. The bases cytosine (C) adenine (A) and guanine (G) are common in both RNA and DNA. However, RNA molecules contain a unique base, uracil (U), while the unique DNA base is thymidine (T). These differences in the base structure markedly affect the secondary structures of these polymers. The structures of DNA and RNA are outlined in Appendix 5.2. 

The nucleic acids (Blackburn and Gait, 1995 Bloomfield et ah, 1999 Saenger, 1983), deoxyribonucleic acids (DNA), and ribonucleic acids (RNA) are polymers of nucleotides which are made up of three parts a purine or pyrimidine base, D-2-deoxyribose for DNA or D-ribose for RNA, and phosphoric acid. The nucleo-... 

The above-mentioned purine-pyrimidine base-pairing scheme consists, as it is well known, of hydrogen bonding between specific, complementary base pairs, namely, adenine-thymine [or uracil in ribonucleic acid (RNA)] and guanine-cytosine (Fig. 1) (shorthand notations A-T or A-U and G-C). The specificity of the bonding concerns both this exclusiveness and the steric arrangement which is... 

As much of the terminology used in molecular biology may be unfamiliar to some readers, it is appropriate to define some of the vocabulary and this is given in an appendix to this chapter. There are two types of nucleic acids, the ribonucleic acids (RNA) and the deoxyribonucleic acids (DNA). Genetic information is carried in the linear sequence of nucleotides in DNA. Each molecule of DNA contains two complementary strands of deoxyribonucleotides which contain the purine bases, adenine and guanine and the pyrimidines, cytosine and thymine. RNA is single-stranded, being composed of a linear sequence of ribonucleotides the bases are the same as in DNA with the exception that thymine is replaced by the closely related base uracil. DNA replication occurs by the polymerisation of a new complementary strand on to each of the old strands. 

BSA was effective for the derivatization of purine and pyrimidine bases [456] and nucleosides [457]. Bases were silylated by heating at 150°C with BSA—acetonitrile (1 3) for 45 min. It was stated that under these conditions the TMS derivative of guanine can be prepared reproducibly, but both cytosine and 5-methylcytosine provided two peaks. Silylation of nucleosides, including pseudouridine, was carried out by heating at 120°C with a 100-fold excess of BSA for 2 h. With the use of OV-17 as the stationary phase, this procedure was adopted for the determination of the composition of ribonucleic acids. 

These purines and pyrimidines join to the sugar-phosphate backbones of nucleic acids through repeating /3-linked AT-glycosidic bonds involving the N9 position of purines and the N1 position of pyrimidines. There are two classes of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). DNA and RNA differ in one of their nitrogenous base components (uracil in RNA, thymine in DNA) and in their sugar (ribose) moiety, as indicated in Fig. V-2. 

The four principal bases of the nucleic acids are uracil and cytosine, which are derivatives of pyrimidine, and adenine and guanine, which are derived from the purine heterocycle (Fig. 15.1). In the nucleic acids, ribose (in ribonucleic acid,... 

The bases found in RNA (ribonucleic acid) are the purine heterocyclics adenine (6-aminopurine) and guanine (2-amino-6-oxypurine) and their complementary pyrimidine bases uracil (2,4-dioxypyrimidine) and cytosine (2-oxy-4-aminopyrimidine), respectively (Section 1, Appendix). In RNA double-stranded duplexes adenine (A) base-pairs with uracil (U) via two hydrogen bonds (A=U) and guanine base-pairs with cytosine (C) via 3 hydrogen bonds (G=C). Adenine forms the nucleoside adenosine by an N-glycosidic link with the... 

Purines and Pyrimidines (fig. 7.1), are best known as building blocks of RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). Adenine and guanine are purine bases (so are xanthine and hypoxanthine, but these are reaction intermediates and are not part of the DNA or RNA molecule). Cytosine, uracil, and thymine are pyrimidine bases. 

The biopolymers DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are present in any living cell and contain or transfer genetic information. They consist ofpurine (adenine, guanine) and pyrimidine bases (cytosine, uracil, thymine) linked to either 2-deoxy-D-ribose (DNA) or D-ribose (RNA). The sugar units are linked together via phosphates (Figure 23). 

The bases found in DNA are either purines (adenine or guanine) or pyrimidines (cytosine or thymine), although some modified bases are found, such as 5 methyl cytosine. Ribonucleic acid contains adenine, cytosine, and guanine as in DNA, but thymine is usually replaced by uracil, which lacks the 5-methyl group present in thymine (Fig. 2.2). In some types of RNA, unlike DNA, modified bases are common. In both DNA and RNA the base is attached through a nitrogen to the... 

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