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Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar ( ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups.
The viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides; they are administered as nucleosides as charged nucleotides cannot easily cross cell membranes. [citation needed] At least one set of new base pairs has been announced as of May 2014. [15]
This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.
Nucleosides are glycosylamines made by attaching a nucleobase to a ribose ring. Examples of these include cytidine , uridine , adenosine , guanosine , thymidine and inosine . Subcategories
For example, dATP stands for deoxyribose adenosine triphosphate. NTPs are the building blocks of RNA, and dNTPs are the building blocks of DNA. [12] The carbons of the sugar in a nucleoside triphosphate are numbered around the carbon ring starting from the original carbonyl of the sugar. Conventionally, the carbon numbers in a sugar are ...
Structure of adenosine 5'-monophosphate (AMP) Structure of guanosine 5'-monophosphate (GMP) Structure of uridine 5'-monophosphate (UMP) Structure of cytidine 5'-monophosphate (CMP) The general structure of a ribonucleotide consists of a phosphate group, a ribose sugar group, and a nucleobase, in which the nucleobase can either be adenine ...
The nucleoside, adenosine, is then deaminated and hydrolyzed to form hypoxanthine via adenosine deaminase and nucleosidase respectively. Hypoxanthine is then oxidized to form xanthine and then uric acid through the action of xanthine oxidase. The other purine nucleoside, guanosine, is cleaved to form guanine.
Synthesis of nucleosides involves the coupling of a nucleophilic, heterocyclic base with an electrophilic sugar. The silyl-Hilbert-Johnson (or Vorbrüggen) reaction, which employs silylated heterocyclic bases and electrophilic sugar derivatives in the presence of a Lewis acid, is the most common method for forming nucleosides in this manner.