Editing Nucleoside

{{Short description|Any of several glycosylamines comprising a nucleobase and a sugar molecule}}
{{Distinguish|nucleotide|nucleobase}}
{{multiple image
| footer            = Two corresponding nucleosides, the [[deoxyribonucleoside]], deoxyadenosine, and the [[ribonucleoside]], adenosine. The line-angle molecular representation implies carbon atoms at each angle, each with enough hydrogen atoms to fill its four-bond valency.
| image1            = Desoxyadenosin.svg|120px
| class1            = skin-invert-image
| alt1              = deoxyadenosine
| caption1          = deoxyadenosine
| image2            = Adenosin.svg|120px
| class2            = skin-invert-image
| alt2              = adenosine
| caption2          = adenosine
}}

'''Nucleosides''' are [[glycosylamine]]s that can be thought of as [[nucleotide]]s 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. In a nucleoside, the [[anomeric]] carbon is linked through a glycosidic bond to the N9 of a [[purine]] or the N1 of a [[pyrimidine]].  Nucleotides are the molecular building blocks of [[DNA]] and [[RNA]].

== List of nucleosides and corresponding nucleobases {{Anchor|List of nucleosides and corresponding nucleobases}}<!--This section is linked at all of the relevant articles, so maintain the anchor here even if the heading wording changes.--> ==

''This list does not include [[Nucleobase#Modified nucleobases|modified nucleobases]] and the corresponding nucleosides'' 

Each chemical has a short symbol, useful when the chemical family is clear from the context, and a longer symbol, if further disambiguation is needed. For example, long nucleobase sequences in genomes are usually described by CATG symbols, not Cyt-Ade-Thy-Gua (see ''[[Nucleic acid sequence#Notation|Nucleic acid sequence § Notation]]''). 

{| border="1" cellpadding="2" cellspacing="0" align="center" style="margin-left:1em" class="skin-invert-image"
|- align="center" valign="bottom"
! Nitrogenous base
! Ribonucleoside
! Deoxyribonucleoside
|- align="center" valign=""
|[[File:Adenin.svg|58px|Chemical structure of adenine]]<br />[[adenine]]<br />symbol '''A''' or '''Ade'''
| [[File:Adenosin.svg|95px|Chemical structure of adenosine]]<br/>[[adenosine]]<br />symbol '''A''' or '''Ado'''
| [[File:Desoxyadenosin.svg|95px|Chemical structure of deoxyadenosine]]<br/>[[deoxyadenosine]]<br/>symbol '''dA''' or '''dAdo'''
|- align="center" valign=""
|[[File:Guanin.svg|86px|Chemical structure of guanine]]<br />[[guanine]]<br />symbol '''G''' or '''Gua'''
| [[File:Guanosin.svg|123px|Chemical structure of guanosine]]<br/>[[guanosine]]<br />symbol '''G''' or '''Guo'''
| [[File:Desoxyguanosin.svg|123px|Chemical structure of deoxyguanosine]]<br/>[[deoxyguanosine]]<br/>symbol '''dG''' or '''dGuo'''
|- align="center" valign=""
|[[File:Thymin.svg|86px|Chemical structure of thymine]]<br />[[thymine]]<br />(5-methyluracil)<br/>symbol '''T''' or '''Thy'''
| [[File:5-Methyluridin.svg|87px|Chemical structure of 5-methyluridine]]<br/>[[5-Methyluridine|5-methyluridine]]<br/>(ribothymidine)<br/>symbol '''m⁵U'''<br/>
| [[File:Desoxythymidin.svg|87px|Chemical structure of thymidine]]<br/>[[thymidine]]<br/>(deoxythymidine)<br/>symbol '''dT''' or '''dThd'''<br/>(dated: '''T''' or '''Thd''')
|- align="center" valign=""
|[[File:Uracil.svg|51px|Chemical structure of uracil]]<br />[[uracil]]<br />symbol '''U''' or '''Ura'''
| [[File:Uridin.svg|87px|Chemical structure of uridine]]<br/>[[uridine]]<br />symbol '''U''' or '''Urd'''
| [[File:Desoxyuridin.svg|87px|Chemical structure of deoxyuridine]]<br/>[[deoxyuridine]]<br/>symbol '''dU''' or '''dUrd'''
|- align="center" valign=""
|[[File:Cytosin.svg|51px|Chemical structure of cytosine]]<br />[[cytosine]]<br />symbol '''C''' or '''Cyt'''
| [[File:Cytidin.svg|87px|Chemical structure of cytidine]]<br/>[[cytidine]]<br />symbol '''C''' or '''Cyd'''
| [[File:Desoxycytidin.svg|87px|Chemical structure of deoxycytidine]]<br/>[[deoxycytidine]]<br />symbol '''dC''' or '''dCyd'''
|-
|}

==Sources==
Nucleosides can be produced from nucleotides [[de novo synthesis|''de novo'']], particularly in the liver, but they are more abundantly supplied via ingestion and digestion of nucleic acids in the diet, whereby [[nucleotidase]]s break down ''[[nucleotide]]s'' (such as the [[thymidine monophosphate]]) into ''nucleosides'' (such as [[thymidine]]) and phosphate. The nucleosides, in turn, are subsequently broken down in the [[lumen (anatomy)|lumen]] of the digestive system by [[nucleosidase]]s into nucleobases and ribose or deoxyribose. In addition, nucleotides can be broken down inside the cell into [[nitrogenous base]]s, and [[ribose-1-phosphate]] or [[deoxyribose-1-phosphate]].

== Use in medicine and technology ==
In medicine several [[nucleoside analogue]]s are used as antiviral or anticancer agents.<ref>{{cite journal |last1=Ramesh |first1=Deepthi |last2=Vijayakumar |first2=Balaji Gowrivel |last3=Kannan |first3=Tharanikkarasu |title=Therapeutic potential of uracil and its derivatives in countering pathogenic and physiological disorders |journal=European Journal of Medicinal Chemistry |date=December 2020 |volume=207 |pages=112801 |doi=10.1016/j.ejmech.2020.112801|pmid=32927231 |s2cid=221724578 }}</ref><ref>{{cite journal |doi=10.1016/S1470-2045(02)00788-X|title=Nucleoside analogues and nucleobases in cancer treatment|year=2002|last1=Galmarini|first1=Carlos M.|last2=MacKey|first2=John R.|last3=Dumontet|first3=Charles|journal=The Lancet Oncology|volume=3|issue=7|pages=415–424|pmid=12142171}}</ref><ref>{{cite journal |doi=10.1038/nrd4010|title=Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases|year=2013|last1=Jordheim|first1=Lars Petter|last2=Durantel|first2=David|last3=Zoulim|first3=Fabien|last4=Dumontet|first4=Charles|s2cid=39842610|journal=Nature Reviews Drug Discovery|volume=12|issue=6|pages=447–464|pmid=23722347}}</ref><ref>{{cite journal |last1=Ramesh |first1=Deepthi |last2=Vijayakumar |first2=Balaji Gowrivel |last3=Kannan |first3=Tharanikkarasu |title=Advances in Nucleoside and Nucleotide Analogues in Tackling Human Immunodeficiency Virus and Hepatitis Virus Infections |journal=ChemMedChem |date=12 February 2021 |volume=16 |issue=9 |pages=1403–1419 |doi=10.1002/cmdc.202000849 |pmid=33427377 |s2cid=231576801 |url=https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/cmdc.202000849 |access-date=13 March 2021 |archive-date=14 December 2021 |archive-url=https://web.archive.org/web/20211214220544/https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/cmdc.202000849 |url-status=dead |url-access=subscription }}</ref> 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 since charged nucleotides cannot easily cross cell membranes.

In molecular biology, several [[nucleic acid analogues|analogues]] of the sugar backbone exist. Due to the low stability of RNA, which is prone to hydrolysis, several more stable alternative nucleoside/nucleotide analogues that correctly bind to RNA are used. This is achieved by using a different backbone sugar. These analogues include [[locked nucleic acid]]s (LNA), [[morpholino]]s and [[peptide nucleic acid]]s (PNA).

In sequencing, [[dideoxynucleotide]]s are used. These nucleotides possess the non-canonical sugar dideoxyribose, which lacks 3' hydroxyl group (which accepts the phosphate).  DNA polymerases cannot distinguish between these and regular deoxyribonucleotides, but when incorporated a dideoxynucleotide cannot bond with the next base and the chain is terminated.

==Prebiotic synthesis of ribonucleosides==

In order to understand how [[life]] arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible [[abiogenesis|prebiotic conditions]].  According to the [[RNA world]] hypothesis free-floating ribonucleosides and ribonucleotides were present in the primitive soup. Molecules as complex as RNA must have arisen from small molecules whose reactivity was governed by physico-chemical processes.  RNA is composed of [[purine]] and [[pyrimidine]] nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian natural selection and [[evolution]]. Nam et al.<ref>{{Cite journal |last1=Nam |first1=Inho |last2=Nam |first2=Hong Gil |last3=Zare |first3=Richard N. |date=2018-01-02 |title=Abiotic synthesis of purine and pyrimidine ribonucleosides in aqueous microdroplets |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=115 |issue=1 |pages=36–40 |doi=10.1073/pnas.1718559115 |pmc=5776833 |pmid=29255025|bibcode=2018PNAS..115...36N |doi-access=free }}</ref> demonstrated the direct condensation of nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing pyrimidine and purine ribonucleosides and ribonucleotides using wet-dry cycles was presented by Becker et al.<ref>{{Cite journal |last1=Becker |first1=Sidney |last2=Feldmann |first2=Jonas |last3=Wiedemann |first3=Stefan |last4=Okamura |first4=Hidenori |last5=Schneider |first5=Christina |last6=Iwan |first6=Katharina |last7=Crisp |first7=Antony |last8=Rossa |first8=Martin |last9=Amatov |first9=Tynchtyk |last10=Carell |first10=Thomas |date=2019-10-04 |title=Unified prebiotically plausible synthesis of pyrimidine and purine RNA ribonucleotides |journal=Science |volume=366 |issue=6461 |pages=76–82 |doi=10.1126/science.aax2747 |pmid=31604305|bibcode=2019Sci...366...76B |s2cid=203719976 |url=https://epub.ub.uni-muenchen.de/71503/1/Science_Becker_2019.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://epub.ub.uni-muenchen.de/71503/1/Science_Becker_2019.pdf |archive-date=2022-10-09 |url-status=live }}</ref>

==See also==
* [[Arabinosyl nucleosides]]
* [[Nucleobase]]
* [[Salvage enzyme]]
* [[Synthesis of nucleosides]]

==References==
{{Reflist}}

==External links==
*{{Commonscatinline|Nucleosides}}

{{Nucleobases, nucleosides, and nucleotides}}
{{Purinergics}}
{{Authority control}}

[[Category:Nucleosides| ]]
[[Category:DNA]]