Nucleosides represent fundamental biomolecules that consist of a nitrogenous base (purine or pyrimidine) linked to a five-carbon sugar (ribose or deoxyribose) via a β-glycosidic bond. Nucleosides function as essential components in nucleic acid synthesis and cellular signaling while being applied in therapeutic treatments.
Nucleotides are phosphorylated nucleosides, forming the building blocks of DNA and RNA. The key distinction is the presence of one or more phosphate groups in nucleotides, enabling them to polymerize into nucleic acids through a phosphodiester bond. The essential distinction between these molecules determines their biological roles and practical uses.
Nucleosides can be categorized based on their sugar moiety and nitrogenous base.
Ribonucleosides contain ribose (with a hydroxyl group at the 2' position) as their sugar component and are the basic building blocks of RNA.
The primary ribonucleosides include:
Ribonucleotides are linked by 3',5'-phosphodiester bonds to form single-stranded RNAs, which are involved in protein synthesis (e.g., mRNA, tRNA). In addition, the 2'-OH of ribose enhances the flexibility of the RNA structure, giving it catalytic (e.g., nuclease) and regulatory functions (e.g., miRNA).
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| Catalog Number | Product Name | Inquiry |
| ONT118003 | Guanosine | Inquiry |
| ONT3080293 | L-Adenosine | Inquiry |
| ONT65463 | Cytidine | Inquiry |
| ONT58968 | Uridine | Inquiry |
Deoxyribosides contain deoxyribose (no hydroxyl group at the 2' position), making them integral to the structure of DNA.
The primary deoxynucleosides include:
The 2'-deoxygenation of deoxyribose reduces the chemical reaction of hydroxyl groups within the molecule and enhances the thermal stability of the double helix structure. Generated by ribonucleoside diphosphate reduction catalyzed by ribonucleotide reductase (RNR), a key step in DNA replication.
Figure 1. Ribonucleoside and deoxynucleoside structures[1].
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| Catalog Number | Product Name | Inquiry |
| ONT958098 | 2'-Deoxyadenosine | Inquiry |
| ONT3992425 | 2'-Deoxycytidine hydrochloride | Inquiry |
| ONT40093945 | Torcitabine (2'-Deoxy-L-cytidine) | Inquiry |
| ONT39967607 | Deoxypseudouridine | Inquiry |
Dideoxynucleosides lack hydroxyl groups at both the 2' and 3' positions of the sugar ring. This absence terminates DNA chain elongation, making them critical in molecular biology and antiviral treatments. Examples include:
In Sanger sequencing, dideoxynucleosides can be used as chain terminators to generate DNA fragments of varying lengths by different fluorescently labeled ddNTP, enabling sequence determination. Another example is in antiretroviral therapy, zidovudine (AZT) blocks viral replication by inhibiting HIV reverse transcriptase activity.
Figure 2. Dideoxynucleosides synthesis example: regioisomers VSM uridine 12.7/12.8 and adenosine 12.9/12.10 were synthesized from the corresponding nucleoside epoxides[2].
The inherent instability and minimal specificity of natural mini-nucleotides require chemical modification to improve their potential as pharmaceutical drugs. While researchers focus on PS modification of the phosphoskeleton in mininucleotides, they also commonly implement modifications to the ribose and base sections of nucleosides. The modified nucleosides and phosphorus reagents are reacted to make nucleic acid monomers (phosphoramidite structure), and the nucleic acid monomers are assembled according to the sequence of the mininucleic acid drug.
Common types of modifications include:
Application Example: The antiviral drug Sofosbuvir targets HCV polymerase through structural changes to uridine. Modified nucleosides function as biomarkers in epigenetics to diagnose cancer at early stages through urine level changes.
Figure 3. Overview of modified nucleosides[3].
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| Catalog Number | Product Name | Inquiry |
| ONT14270736 | 5'-O-Triphenylmethyl-2'-deoxyuridine | Inquiry |
| ONT136834214 | DMT-2'-F-Bz-dA | Inquiry |
| ONT2306782647 | 2'-O-Methyl-8-methyl guanosine(m8Gm) | Inquiry |
| ONT23197888 | 3'-O-Acetyl-2'-deoxyuridine | Inquiry |
Nucleosides perform several vital biological roles:
A. Genetic Information Transfer - Precursor molecules in DNA and RNA synthesis
B. Cellular Energy Transfer - ATP, GTP, and UTP function as cellular energy carriers
C. Signal Transduction - cAMP and cGMP act as second messengers in signaling pathways
D. Neurotransmission & Immune Modulation - Adenosine influences sleep, cognition, and immune responses
E. Enzyme Cofactors - NAD+, FAD, and CoA are nucleoside-derived cofactors in metabolic pathways
Antiviral and Antitumor Therapeutics
Nucleoside analogs serve as critical agents in antiviral and cancer treatments.
| Drug | Application | Mechanism |
| Zidovudine (AZT) | HIV therapy | Reverse transcriptase inhibitor |
| Remdesivir | SARS-CoV-2 | RNA polymerase inhibitor |
| Gemcitabine | Pancreatic cancer | DNA synthesis inhibitor |
| Cytarabine | Leukemia | DNA polymerase inhibitor |
Molecular Biology and Sequencing Technologies
Nutraceutical and Industrial Uses
Q1: What is the difference between ribonucleosides and deoxynucleosides?
A1: The primary difference between ribonucleosides and deoxynucleosides is that ribonucleosides have ribose sugars, while deoxynucleosides possess deoxyribose sugars.
Q2: How do dideoxynucleosides function in antiviral treatments?
A2: ddN nucleosides stop DNA synthesis because they lack a 3'-OH group, which stops viral replication as demonstrated in HIV and hepatitis B treatments.
Q3: What are modified nucleosides used for?
A3: Modified nucleosides work to stabilize nucleic acids and increase drug effectiveness while controlling biological functions during cancer therapy and RNA-based treatment development.
Q4: Are nucleosides used in nutritional supplements?
A4: Yes, nucleosides are added to infant formula and animal feed to support immune function and metabolic processes.
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References
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