Nucleoside


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nucleoside

[′nü·klē·ə‚sīd]
(biochemistry)
The glycoside resulting from removal of the phosphate group from a nucleotide; consists of a pentose sugar linked to a purine or pyrimidine base.

Nucleoside

 

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.

I. B. ZBARSKH

References in periodicals archive ?
Although most cells are capable of de novo nucleoside biosynthesis, the cellular nucleotide pool is preferentially maintained via the more energy efficient "salvage pathway" involving recycling and uptake of extracellular hydrophilic nucleosides by specialized integral membrane proteins, termed nucleoside transporters (NTs) (Molina-Arcas et al.
A novel nucleoside reverse transcriptase inhibitor candidate - EFdA (4'-ethynyl-2-fluoro-2'-deoxyadenosine) - has shown antiviral activity toward highly resistant HIV strains.
We discovered the structure of the transporter molecule, and now we believe it is possible to improve nucleoside drugs to be better recognized by a particular form of the transporter molecule that resides in certain types of tissue.
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.
Neither Videx nor any other nucleoside had any impact on cardiovascular disease risk or on these heart disease markers.
TORONTO -- A large, randomized comparison of three standard regimens for initial treatment of HIV has shown that all are safe and effective, but a regimen of efavirenz plus two nucleosides was significantly better at reducing HIV viral load, investigators said at the 16th International AIDS Conference.
Reverset is a nucleoside analog reverse transcriptase inhibitor that is being developed as a once-daily oral HIV therapy by Incyte Corporation and Pharmasset, Inc.
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).
Approved June 24, 1996 for use in combination with nucleoside analogues for the treatment of HIV-infected adults experiencing clinical and/or immunologic deterioration.
A new kind of medication now in clinical trials blocks reverse transcriptase by attaching not at its nucleoside binding site, but in a different spot.
Nasdaq: ISIS) with nucleoside phosphoramidites at quantities up to 100 kg.
Importantly, GL59728 was also tested in combination with other classes of HCV antiviral compounds, including a nucleoside chain terminator, a protease inhibitor and interferon alpha, and shown to be additive in activity with each.

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