|
}}
'''Pirimidina''' ({{lang-en|Pyrimidine}}) adalah suatu [[senyawa organik]] [[heterosiklik]] [[aromatik]] yang mirip dengan [[piridina]].<ref name="isbn0-582-27843-0">{{cite book |author=Gilchrist, Thomas Lonsdale; Gilchrist, T. L. |authorlink= |editor= |others= |title=Heterocyclic chemistry |edition= |language= |publisher=Longman |location=New York |year=1997 |origyear= |pages= |quote= |isbn=0-582-27843-0 |oclc= |doi= |url= |accessdate=}}</ref> Satu dari tiga [[diazina]] (senyawa heterosiklik enam [[karbon]] dengan dua [[nitrogen]] pada cincin), mempunyai [[nitrogen]] pada posisi 1 dan 3 dalam cincin.<ref name="JouleMills5thp250">{{cite book | title=Heterocyclic Chemistry |edition=5th |editor1-last=Joule |editor1-first=John A. |editor2-last=Mills |editor2-first=Keith |publisher=Wiley |location=Oxford |year=2010 |page=250 |quote= |isbn=978-1-405-13300-5 |oclc= |doi= |url= |accessdate=}}</ref> Kedua diazina lain adalah [[pirazina]] (nitrogen pada posisi 1 dan 4) dan [[piridazina]] ( pada posisi 1 dan 2). Dalam [[asam nukleat]], ketiga tipe [[nukleobasabasa nukleotida]] merupakan derivat [[pirimidin]] yaitu: [[sitosina|sitosina (= cytosine)]] (C), [[timina]] (T), dan [[urasil]] (U).
== Keberadaan dan sejarah ==
[[FileBerkas:PinnerPyrimidin.png|thumbjmpl|leftkiri|77px|Struktur pirimidina menurut Pinner (1885).]]
Sistem cincin pirimidina banyak dijumpai dalam alam<ref name=Lagoja1>{{Cite journal
| author = Lagoja, Irene M.
| doi = 10.1002/cbdv.200490173
| pmid = 17191918
| access-date = 2014-12-13
| archive-date = 2017-02-15
| archive-url = https://web.archive.org/web/20170215012342/http://homepage.univie.ac.at/mario.barbatti/papers/pyrazine_pyrimidine/pyrimidine.pdf
| dead-url = yes
}}</ref>
sebagai senyawa berfusi substitusi dan cincin serta derivatifnya, termasuk [[#Nukleotida|nukleotida]], [[tiamina]] (vitamin B1) dan [[alloxan]]. Juga didapati dalam banyak senyawa sintetik seperti [[barbiturat]] dan obat [[HIV]], [[zidovudine]]. Meskipun derivatif pirimidina seperti [[asam urat]] dan alloxan telah dikenal sejak awal abad ke-19, sintesis pirimidina dalam laboratorium baru dilakukan pada tahun 1879,<ref name=Lagoja1/> ketika Grimaux melaporkan pembuatan [[asam barbiturat]] dari [[urea]] Ivy dan [[asam malonat]] dengan katalis [[fosfor oxiklorida]].<ref name=Grimaux1879>{{Cite journal
| title = Pyrimidine as Constituent of Natural Biologically Active Compounds
}}</ref> ketika Grimaux melaporkan pembuatan [[asam barbiturat]] dari [[urea]] Ivy dan [[asam malonat]] dengan katalis [[fosfor oxiklorida]].<ref name=Grimaux1879>{{Cite journal
| author = Grimaux, E.
| year = 1879
| url = http://visualiseur.bnf.fr/ark:/12148/bpt6k30457/f85.image
}}</ref>
Studi sistematik pirimidina dimulai<ref name="ElderfieldVol6">{{cite book |author= Kenner, G.W.; Todd, Sir Alexander |editor = Elderfield, R.C. |title=Heterocyclic Compounds, Volume 6 |publisher=Wiley |location=New York |year=1957 |pages=235 |oclc= |doi= |url= |accessdate=}}</ref> pada tahun 1884 oleh [[Adolf Pinner|Pinner]],<ref name=Pinner1884>{{Cite journal
| author = [[Adolf Pinner|Pinner, A.]]
| year = 1884
melalui konversi [[asam barbiturat]] menjadi 2,4,6-trikloropirimidina diikuti oleh reduksi menggunakan debu [[seng]] dalam air panas.
== Nomenklatur ==
Nomenklatur pirimidina tergolong sederhana. Namun, sebagaimana heterosiklik lainnya, gugus hidroksil tautomerik menghasilkan komplikasi karena mereka adanya terutama dalam bentuk amida siklik. Misalnya, 2-hidroksipirimidina lebih tepat dinamai [struktur] 2-pirimidon. Tersedia daftar sebagian nama-nama trivial dari berbagai pirimidina.<ref name="BrownPyrimidines1994p5">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=5–6[https://archive.org/details/pyrimidines0000unse/page/5 5]–6|isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
== Sifat fisika ==
Sifat-sifat fisika dapat dilihat pada kotak info. Diskusi lebih mendalam, termasuk spektrum, dapat dilihat dalam Brown ''et al.''<ref name="BrownPyrimidines1994p242">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=242–244[https://archive.org/details/pyrimidines0000unse/page/242 242]–244|isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
== Sifat kimia ==
Menurut klasifikasi Albert<ref name="Albert1968p56">{{cite book |author=Albert, Adrien |title=Heterocyclic Chemistry, an Introduction |publisher=Athlone Press |location=London |year=1968 |pages=56–62[https://archive.org/details/heterocyclicchem0000albe/page/56 56]–62|isbn= |url= https://archive.org/details/heterocyclicchem0000albe|accessdate=}}</ref> heterosiklik enam karbon dapat dikatakan "π-deficient" ("kekurangan π"). Substitusi oleh gugus [[Elektronegativitas|elektronegatif]] atau atom nitrogen tambahan dalam cincin secara signifikan meningkatkan "kekurangan π" itu. Efek ini juga menurunkan kadar basa.<ref name="Albert1968p437">{{cite book |author=Albert, Adrien |title=Heterocyclic Chemistry, an Introduction |publisher=Athlone Press |location=London |year=1968 |pages=437–439[https://archive.org/details/heterocyclicchem0000albe/page/437 437]–439|isbn= |url= https://archive.org/details/heterocyclicchem0000albe|accessdate=}}</ref>
Sebagaimana piridina, dalam pirimidina densitas elektron π menurun sampai taraf lebih besar. Karenanya, [[substitusi aromatik elektrofilik]] lebih sulit sementara [[substitusi aromatik nukleofilik]] terbantu. Contoh jenis reaksi terakhir adalah penghilangan gugus [[amino]] dalam 2-aminopirimidina oleh [[klorinaklor]].<ref>[[Organic Syntheses]], Coll. Vol. 4, p.182 (1963); Vol. 35, p.34 (1955) [http://www.orgsynth.org/orgsyn/pdfs/CV4P0182.pdf Link]</ref> dan reaksi sebaliknya.<ref>[[Organic Syntheses]], Coll. Vol. 4, p.336 (1963); Vol. 35, p.58 (1955) [http://www.orgsynth.org/orgsyn/pdfs/CV4P0336.pdf Link]</ref>
Ketersediaan pasangan elektron tunggal ([[kadar basa]]) menurun dibandingkan [[piridina]]. Dibandingkan piridina, [[N-alkilasi]] dan [[N-oksidasi]] lebih sulita. Nilai [[pKa]] untuk pirimidina terprotonasi adalah 1,23 dibandingkan 5,30 untuk piridina. Protonasi dan tambahan elektrofilik lain akan terjadi pada hanya satu [[nitrogen]] karena deaktivasi lebih lanjut oleh nitrogen kedua.<ref name="JouleMills5thp250">{{cite book |author=Joule, J. A.; Mills, K. |publisher=Wiley |location=Oxford |year=2010 |pages=250 |isbn=978-1-405-133300-5 }}</ref> Posisi 2-, 4-, dan 6- pada cincin pirimidina merupakan analog kekurangan elektron dari senyawa pyridina dan nitro- serta dinitrobenzena. Posisi 5 lebih rendah tingkat kekurangan elektronnya dan substituen di sana sangat stabil. Namun, substitusi eletrofilik relatif lancar pada posisi 5, termasuk [[nitrasi]] dan halogenasi.<ref name="BrownPyrimidines1994p4">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=4–8[https://archive.org/details/pyrimidines0000unse/page/4 4]–8|isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
Reduction in [[resonance stabilization]] of pyrimidines may lead to addition and ring cleavage reactions rather than substitutions. One such manifestation is observed in the [[Dimroth rearrangement]].
Reduksi dalam [[stabilisasi resonansi]] pirimidina dapat lebih menghasilkan [[reaksi adisi]] dan pemutusan cincin daripada substitusi. Salah satu manifestasinya dapat diamati pada "[[Dimroth rearrangement]]".
Pyrimidine is also found in meteorites, but scientists still do not know its origin. Pyrimidine also photolytically decomposes into [[uracil]] under UV light.<ref name="pmid19778279">{{cite journal |author=Nuevo M, Milam SN, Sandford SA, Elsila JE, Dworkin JP |title=Formation of uracil from the ultraviolet photo-irradiation of pyrimidine in pure H<sub>2</sub>O ices |journal=Astrobiology |volume=9 |issue=7 |pages=683–695 |year=2009 |pmid=19778279 |doi=10.1089/ast.2008.0324|bibcode = 2009AsBio...9..683N }}</ref> ▼
▲PyrimidinePirimidina isjuga alsoditemukan foundpada in meteorites[[meteorit]], buttetapi scientistspara stillilmuwan domasih nottidak knowtahu itsasal originusulnya. PyrimidinePirimidina alsojuga photolyticallysecara decomposesfotolitik intomengalami dekomposisi menjadi [[ uracilurasil]] underdi UVbawah lightcahaya [[UV]].<ref name="pmid19778279">{{cite journal |author=Nuevo M, Milam SN, Sandford SA, Elsila JE, Dworkin JP |title=Formation of uracil from the ultraviolet photo-irradiation of pyrimidine in pure H<sub>2</sub>O ices |journal=Astrobiology |volume=9 |issue=7 |pages=683–695 |year=2009 |pmid=19778279 |doi=10.1089/ast.2008.0324|bibcode = 2009AsBio...9..683N }}</ref>
== Synthesis ==
As is often the case with parent heterocyclic ring systems, the synthesis of pyrimidine is not that common and is usually performed by removing functional groups from derivatives. Primary syntheses in quantity involving [[formamide]] have been reported.<ref name="BrownPyrimidines1994p241">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=241–2 |isbn=0-471-50656-7|url= |accessdate=}}</ref> ▼
== Sintesis ==
As a class, pyrimidines are typically synthesized by the “Principal Synthesis” involving cyclization of beta-dicarbonyl compounds with N-C-N compounds. Reaction of the former with amidines to give 2-substituted pyrimidines, with urea to give 2-pyrimidiones, and guanidines to give 2-aminopyrimidines are typical.<ref name="BrownPyrimidines1994p149">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=149–239 |isbn=0-471-50656-7|url= |accessdate=}}</ref> ▼▲AsSebagaimana issering oftenkali thedijumpai casepada withsistem parentheterosiklik heterocyclic ring systemsinduk, thesintesis synthesispirimidina oftidak pyrimidinebegitu islazim notdan thatbiasanya commondilakukan anddengan ismenghilangan usually[[gugus performedfungsi]] bydari removing functional groups from derivativesderivatif. Sintesis Primaryprimer synthesesdalam injumlah quantitybesar involvingmelibatkan [[ formamideformamida]] have beentelah reporteddilaporkan.<ref name="BrownPyrimidines1994p241">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages= 241–2[https://archive.org/details/pyrimidines0000unse/page/241 241]–2|isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
Pyrimidines can be prepared via the [[Biginelli reaction]]. Many other methods rely on [[condensation]] of [[carbonyl]]s with diamines for instance the synthesis of 2-Thio-6-methyluracil from [[thiourea]] and [[ethyl acetoacetate]] <ref>[[Organic Syntheses]], Coll. Vol. 4, p.638 (1963); Vol. 35, p.80 (1955) [http://www.orgsynth.org/orgsyn/pdfs/CV4P0638.pdf Link]</ref> or the synthesis of 4-methylpyrimidine with 4,4-dimethoxy-2-butanone and [[formamide]].<ref>[[Organic Syntheses]], Coll. Vol. 5, p.794 (1973); Vol. 43, p.77 (1963) [http://www.orgsynth.org/orgsyn/pdfs/CV5P0794.pdf Link]</ref> ▼
▲AsSebagai asuatu classkelas, pyrimidinespirimidina arebiasanya typicallydisintesis synthesized by themelalui “Principal Synthesis” involvingmelibatkan cyclizationsiklisasi ofsenyawa beta- dicarbonyldikarbonil compoundsdengan withsenyawa N-C-N compounds. Reaksi Reactionsebelumnya ofdengan theamidina formermenghasilkan withsubstitusi amidinespirimidina topada giveposisi 2 -substituted pyrimidines, withbiasanya dengan urea to givemenghasilkan 2- pyrimidionespirimidion, anddan guanidinesdengan toguanidina givemenghasilkan 2- aminopyrimidines are typicalaminopirimidina.<ref name="BrownPyrimidines1994p149">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages= 149–239[https://archive.org/details/pyrimidines0000unse/page/149 149]–239|isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
▲PyrimidinesPirimidina candapat bedibuat prepared via themelaui [[Biginelli reaction]]. ManyBanyak othermetoda methodslain relybergantung onpada [[ condensationkondensasi]] of [[ carbonylkarbonil]] s withdengan diamines for instance thediamina, synthesismisalnya ofsintesis 2- Thiothio-6- methyluracilmetilurasil fromdari [[thiourea]] anddan [[ ethyletil acetoacetateasetoasetat]] <ref>[[Organic Syntheses]], Coll. Vol. 4, p.638 (1963); Vol. 35, p.80 (1955) [http://www.orgsynth.org/orgsyn/pdfs/CV4P0638.pdf Link]</ref> or the synthesisatau ofsintessi 4- methylpyrimidinemetilpirimidina withdengan 4,4- dimethoxydimetoksi-2- butanonebutanon anddan [[ formamideformamida]].<ref>[[Organic Syntheses]], Coll. Vol. 5, p.794 (1973); Vol. 43, p.77 (1963) [http://www.orgsynth.org/orgsyn/pdfs/CV5P0794.pdf Link]</ref>
<!--
A novel method is by reaction of certain [[amide]]s with [[carbonitrile]]s under electrophilic activation of the amide with 2-chloro-pyridine and [[trifluoromethanesulfonic anhydride]]:<ref>''Single-Step Synthesis of Pyrimidine Derivatives'' Mohammad Movassaghi and Matthew D. Hill [[J. Am. Chem. Soc.]]; '''2006'''; 128(44) pp 14254–14255; (Communication) {{DOI|10.1021/ja066405m}}</ref>
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:[[ ImageBerkas:PyrimidineSynthAmideCarbonitrile.png|400px| PyrimidineSintesis Synthesispirimidina, Movassaghi (2006 )]] ▼
== Reaksi ==
▲:[[Image:PyrimidineSynthAmideCarbonitrile.png|400px|Pyrimidine Synthesis Movassaghi 2006]]
BecauseKarena ofmenurunnya thekadar decreasedbasa basicitydibandingkan compared to pyridinepiridina, electrophilicsubstitusi substitutionelektrofilik ofpirimidina pyrimidinekurang is less facilelancar. [[ ProtonationProtonasi]] oratau [[ alkylationalkilasi]] typicallybiasanya takesberlangsung placepada athanya onlysatu one of the ringatom nitrogen atomsdalam cincin. [[Oksidasi-N]] Mono N-oxidationmono occursterjadi bymelalui reactionreaksi withdengan peracidsperasida.<ref name="JouleMills5thp253">{{cite book | title=Heterocyclic Chemistry |edition=5th |editor1-last=Joule |editor1-first=John A. |editor2-last=Mills |editor2-first=Keith |publisher=Wiley |location=Oxford |year=2010 |pages=253–4 |quote= |isbn=978-1-405-13300-5 |oclc= |doi= |url= |accessdate=}}</ref> ▼<!--
Substitusi-C eletrofilik pirimidina terjadi pada posisi 5, yang paling rendah tingkat kekurangan elektronnya. Nitration, [[nitrosation]], [[azo coupling]], halogenation, [[sulfonation]], formylation, hydroxymethylation, and aminomethylation have been observed with substituted pyrimidines.<ref name="BrownPyrimidines1994p9">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=[https://archive.org/details/pyrimidines0000unse/page/9 9]–13 |isbn=0-471-50656-7|url=https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
Nucleophilic C-substitution should be facilitated at the 2-, 4-, and 6-positions but there are only a few examples. Amination and hydroxylation has been observed for substituted pyrimidines. Reactions with Grignard or alkyllithium reagents yield 4-alkyl- or 4-aryl pyrimidine after aromatization.<ref name="BrownPyrimidines1994p14">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages= 14–15[https://archive.org/details/pyrimidines0000unse/page/14 14]–15 |isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref> ▼==Reactions==
▲Because of the decreased basicity compared to pyridine, electrophilic substitution of pyrimidine is less facile. [[Protonation]] or [[alkylation]] typically takes place at only one of the ring nitrogen atoms. Mono N-oxidation occurs by reaction with peracids.<ref name="JouleMills5thp253">{{cite book | title=Heterocyclic Chemistry |edition=5th |editor1-last=Joule |editor1-first=John A. |editor2-last=Mills |editor2-first=Keith |publisher=Wiley |location=Oxford |year=2010 |pages=253–4 |quote= |isbn=978-1-405-13300-5 |oclc= |doi= |url= |accessdate=}}</ref>
ElectrophilicFree C-substitutionradical ofattack has been observed for pyrimidine occursand atphotochemical thereactions 5-position,have thebeen leastobserved electronfor deficientsubstituted pyrimidines.<ref name="BrownPyrimidines1994p15">{{cite Nitration,book [[nitrosation]]|author=Brown, [[azoD. coupling]],J.; halogenationEvans, [[sulfonation]],R.F.; formylationCowden, hydroxymethylationW. B.; Fenn, andM. aminomethylationD. have|title=The beenPyrimidines observed|pages=15–16 with}}</ref> substituted pyrimidinesPyrimidine can be hydrogenated to give tetrahydropyrimidine.<ref name="BrownPyrimidines1994p9BrownPyrimidines1994p17">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=9–13[https://archive.org/details/pyrimidines0000unse/page/17 17] |isbn=0-471-50656-7|url= https://archive.org/details/pyrimidines0000unse|accessdate=}}</ref>
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== Nukleotida ==
▲Nucleophilic C-substitution should be facilitated at the 2-, 4-, and 6-positions but there are only a few examples. Amination and hydroxylation has been observed for substituted pyrimidines. Reactions with Grignard or alkyllithium reagents yield 4-alkyl- or 4-aryl pyrimidine after aromatization.<ref name="BrownPyrimidines1994p14">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=14–15 |isbn=0-471-50656-7|url= |accessdate=}}</ref>
[[ FileBerkas:Blausen 0324 DNA Pyrimidines.png| thumbjmpl|250px| The pyrimidineBasa nitrogen basespirimidina nitrogen founddijumpai indalam [[DNA ]] anddan [[RNA ]].]] ▼
ThreeTiga [[nucleobase]] s foundyang inditemukan dalam [[ nucleicasam acidnukleat]] s, yaitu [[ sitosina|sitosina/cytosine]] (C), [[ thyminetimina]] (T), anddan▼Free radical attack has been observed for pyrimidine and photochemical reactions have been observed for substituted pyrimidines.<ref name="BrownPyrimidines1994p15">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |pages=15–16 }}</ref> Pyrimidine can be hydrogenated to give tetrahydropyrimidine.<ref name="BrownPyrimidines1994p17">{{cite book |author=Brown, D. J.; Evans, R.F.; Cowden, W. B.; Fenn, M. D. |title=The Pyrimidines |publisher=John Wiley & Sons |location=New York |year=1994 |pages=17 |isbn=0-471-50656-7|url= |accessdate=}}</ref>
[[urasil]] (U), merupakan derivatif pirimidina:
== Nucleotides ==
▲[[File:Blausen 0324 DNA Pyrimidines.png|thumb|250px|The pyrimidine nitrogen bases found in DNA and RNA.]]
▲Three [[nucleobase]]s found in [[nucleic acid]]s, [[cytosine]] (C), [[thymine]] (T), and
[[uracil]] (U), are pyrimidine derivatives:
{|
|-
| [[ImageBerkas:Cytosine chemical structure.png|leftkiri|101px|ChemicalStruktur structure ofkimia cytosinesitosina]] || [[ImageBerkas:Thymine chemical structure.png|leftkiri|127px|ChemicalStruktur structure ofkimia thyminetimina]] || [[ImageBerkas:Uracil chemical structure.png|leftkiri|102px|Chemical structureStruktur ofkimia uracilurasil]]
|-
| <center>Sitosina/Cytosine ('''C''')</center> || <center>ThymineTimina ('''T''')</center> || <center>UracilUrasil ('''U''')</center>
|}
InDalam [[DNA]] anddan [[RNA]], thesebasa-basa basesini formmembentuk [[hydrogenikatan bondhidrogen]]s withdengan their[[purina]] [[:en:complementarity (molecular biology)|complementarykomplementer]] [[purine]]s. ThusJadi, indalam DNA, thesenyawa [[purinespurina]] [[adenineadenina]] (A) anddan [[guanineguanina]] (G) pairmasing-masing upberpasangan withdengan thesenyawa pyrimidinespirimidina thyminetimina (T) anddan cytosinesitosina (C), respectively.membentuk pasangan-pasangan A:T dan G:C.
In [[RNA]], the complement of [[adenine]] (A) is [[uracil]] (U) instead of [[thymine]] (T), so the pairs that form are [[adenine]]:[[uracil]] and [[guanine]]:[[cytosine]].
Dalam [[RNA]], komplemen [[adenina]] (A) adalah [[urasil]] (U) bukannya [[timina]] (T), sehingga pasangan yang dibentuk adalah [[adenina]]:[[urasil]] (A:U) dan [[guanina]]:[[sitosina]] (G:C).
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Very rarely, thymine can appear in RNA, or uracil in DNA. Other than the three major pyrimidine bases presented, some minor pyrimidine bases can also occur in [[nucleic acids]]. These minor pyrimidines are usually [[Methylation|methylated]] versions of major ones and are postulated to have regulatory functions.<ref>Nelson David L. and Michael M. Cox. ''Principles of Biochemstry'', ed. 5. W.H. Freeman and Company (2008) p. 272–274.</ref>
{{Reflist|2}}
{{Nukleobasa, nukleosida, dan nukleotida}}
{{Nucleobases, nucleosides, and nucleotides}}
[[Kategori:Pirimidina| ]]
[[Category:Biomolecules]]
[[Kategori:Basa aromatik]]
[[Category:Pyrimidines]]
[[Kategori:Cincin aromatik sederhana]]
[[Category:Aromatic bases]]
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