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The glycoside resulting from removal of the phosphate group from a nucleotide; consists of a pentose sugar linked to a purine or pyrimidine base.



a compound that consists of a nitrogenous base and a carbohydrate. A nucleoside whose carbohydrate portion is ribose is called a ribonucleoside, and a deoxyribose-containing nucleoside is called a deoxyribonucleoside. Nucleosides have the following structural formula:

In deoxyribonucleosides, X is replaced by a hydrogen atom, while in ribonucleosides, a hydroxyl group replaces X. R can be any purine or pyrimidine base.

A nucleoside can be regarded as the product of the dephos-phorylation of a nucleotide. In a nucleoside, the purine or pyrimidine base is connected to the 1′ carbon atom by a β-glycoside bond. Nucleosides are named according to their base; thus, adenosine contains adenine, guanosine—guanine, uridine—uracil, cytidine—cytosine, and thymidine—thymine. The nucleosides that contain hypoxanthine and xanthine are called inosine and xanthosine, respectively. A few other nucleosides exist, which are structurally similar to those mentioned but which differ in the particular base, carbohydrate component, or type of internal bonds.

Free nucleosides are present in small quantities in several biological substances. The significance of most nucleosides, however, is their occurrence as constituents of nucleotides and nucleic acids.


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The team determined the chemical and physical principles a transporter molecule uses to recognize the nucleosides, "so if you can improve the interactions between the transporter and the drug, you won't need as much of the drug to get it into the tumor cells efficiently," Lee said.
RG7128, a nucleoside analog for chronic HCV infection, is in two Phase 2b clinical trials in combination with Pegasys(R) plus Copegus(R) and is also in the INFORM studies, the first series of studies designed to assess the potential of combinations of small molecules without Pegasys(R) and Copegus(R) to treat chronic HCV.
In other words, although the risk of heart disease was higher in people who took Ziagen than in those taking other nucleosides, their overall risk of heart disease was still small.
Participants were randomized equally to one of three arms: lopinavir soft gel capsules plus two nucleosides, efavirenz plus two nucleosides, and lopinavir soft gel capsules plus efavirenz.
Also, TDM cannot be used for nucleosides because of their intracellular activity (blood plasma levels may not accurately be a reflection of drug penetration and therapeutic activity).
Chemists usually synthesize new nucleosides by modifying naturally existing ones.
The Company believes that its protides possess several pharmacological advantages over nucleosides alone and potentially other nucleotide prodrugs.
The new products, namely 3'- Amino-2',3'-A and G nucleosides serve as building blocks for oligonucleotides, which are resistant to enzymatic degradation.
Similar results were reported from a longer-term study in which 62 patients who had been on indinavir (Crixivan)/efavirenz (Sustiva) regimens for at least 18 months were randomly switched to either efavirenz and two nucleosides or to ritonavir-boosted lopinavir and efavirenz.
With these caveats, we now have a lot of confidence in Sustiva and two nucleosides.
Linking [5-hydroxycytidine] to an RNA world is a little premature" because such modified nucleosides are not necessarily "old" in an evolutionary sense, says biochemist Andrew D.

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