Nucleosides, nucleotides nomenclature

Currently, three categories of anti-HCV DAAs have been approved, and the nomenclature is based on which viral function is inhibited or affected. The categories are NS3/NS4A protease inhibitors [PI, e.g., boceprevir (2), telaprevir (3), and simeprevir (4)], NS5A protein inhibitors [e.g., ledipasvir (5)], and NS5B RNA-dependent RNA polymerase (RdRp) inhibitors (e.g., sofosbuvir). The last category can be divided further into two subclasses nucleoside/nucleotide polymerase inhibitors (NPI) and nonnucleoside polymerase inhibitors (NNPI). 

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. 

The nomenclature for the commonly found bases, nucleosides, and nucleotides is shown in Tables I-l-2a and -2b. Note that the deoxy part of the names deoxythymidine, dTMP, etc., is sometimes understood, and not expressly stated, because thymine is almost always found attached to deoxyribose. 

Table 20.1 Classification and nomenclature of bases, nucleosides and nucleotides...

Bases, Nucleosides, and Nucleotides. The relationship of these components of a nucleic acid or polynucleotide is shown in Chart 10. The numbering of the pyrimidine (uracil) and the purine (adenine) shown is the IUPAC nomenclature used by Chemical Abstracts, and... 

Both DNA and RNA contain two major purine bases, adenine (A) and guanine (G), and two major pyrimidines. In both DNA and RNA one of the pyrimidines is cytosine (C), but the second major pyrimidine is not the same in both it is thymine (T) in DNA and uracil (U) in RNA Only rarely does thymine occur in RNA or uracil in DNA The structures of the five major bases are shown in Figure 8-2, and the nomenclature of their corresponding nucleotides and nucleosides is summarized in Table 8-1. 

Table 10 The Nucleic Bases, Their Proton Ionization Constants (pit,), and the Nomenclature of Their Nucleoside and Nucleotide Derivatives...

The nomenclature of nucleotides and their constituent units was presented earlier (Section 5.1.2). Recall that a nucleoside consists of a purine or pyrimidine base linked to a sugar and that a nucleotide is a phosphate ester of a nucleoside. The names of the major bases of RNA and DNA, and of their nucleoside and nucleotide derivatives, are... 

Structure of the nucleotide in DNA and RNA. The base adenine is used as an example. See Table 27-1 for a complete nomenclature of nucleosides and nucleotides. 

Table 27-1 gives the nomenclature of purine and pyrimidine nucleosides and nucleotides. Names of purine nucleosides end in -osine, whereas those of pyrimidine nucleosides end in -idine guanine nucleoside is guanosine and should not be confused with guanidine, which is not a nucleic acid base thymidine is a deoxyriboside. 

There is another pnrine derivative of crucial biochemical importance - adenosine triphosphate (ATP). This substance is a carrier of energy, for when a phosphate link is broken, a large amount of energy is released. Note some trivial nomenclature the moieties produced by linking one of the heterocyclic bases to a ribose or 2 -deoxyribose sugar, are known as nucleosides (e.g. adenosine, guanosine, cytidine, thymidine). A nncleotide is a 5 -phosphate (or di- or tri-phosphate) of a nucleoside - ATP is a nucleotide. 

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