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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.


References in periodicals archive ?
Our observations that BNO-1055 and its S2 sub-fraction primarily inhibit the salvage uptake of extracellular nucleosides are in line with reports that cimicifugoside isolated from a related species C.
They found that both the human and bacterial transporter use a sodium gradient to import nucleosides and drugs into the cells.
1) This research compared Ml rates in people who took the nucleosides Ziagen, Videx (didano-sine), Epivir, Zerit (stavudine), or Retrovir.
With a median follow-up of 112 weeks, the time to virologic failure was significantly shorter in the lopinavir plus two nucleosides arm, compared with the efavirenz plus two nucleosides arm.
Until recently the only approved form of therapy for HIV infection was treatment with drugs from the class of nucleoside analogue reverse transcriptase inhibitors (see Table 1), often referred to as RT inhibitors or nucleoside analogues.
He and Hager took a completely different tack that allowed them to avoid nucleosides altogether and to use starting materials that can be mass produced inexpensively.
Follow-up data from 46 patients studied for a median of 104 weeks showed a median gain compared with baseline of 782 g of limb fat among the nonnucleoside patients and a median 900-g loss among patients receiving nucleosides.
Both these mutations can cause cross-resistance to other nucleoside analogs.
BARCELONA, SPAIN -- Tenofovir, a nucleoside reverse transcriptase inhibitor, was as effective as stavudine, a standard nucleoside reverse transcriptase inhibitor, when used as part of initial HIV treatment.
Cech of the University of Colorado in Boulder also points out that the enzyme-like agent s only a modified nucleoside -- not a "proper ribozyme," or folded chain of RNA nucleosides that binds a substance to foster a specific biochemical reaction.

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