Editing Guanine

{{Short description|Chemical compound of DNA and RNA}}
{{Distinguish|Guanosine|Guanidine|Guanfacine|Guanamine|Guanín}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 443850318
| ImageFile1 = Guanin.svg
| ImageSize1 = 150px
| ImageClass1 = skin-invert-image
| ImageFileL2 = Guanine-3D-balls.png
| ImageFileR2 = Guanine-3D-vdW.png
| PIN = 2-Amino-1,9-dihydro-6''H''-purin-6-one
| OtherNames = 2-amino-6-hydroxypurine,<br />2-aminohypoxanthine,<br />Guanine
|Section1={{Chembox Identifiers
| IUPHAR_ligand = 4556
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB02377
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 16235
| SMILES = N1C(N)=NC=2NC=NC2C1=O
| SMILES_Comment = keto form
| SMILES1 = OC1=C2N=CNC2=NC(=N1)N
| SMILES1_Comment = enol form
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 5Z93L87A1R
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C00242
| InChI = 1/C5H5N5O/c6-5-9-3-2(4(11)10-5)7-1-8-3/h1H,(H4,6,7,8,9,10,11)
| InChIKey = UYTPUPDQBNUYGX-UHFFFAOYAE
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 744
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 219568
| PubChem = 135398634
| EC_number = 200-799-8
| Beilstein = 147911
| Gmelin = 431879
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C5H5N5O/c6-5-9-3-2(4(11)10-5)7-1-8-3/h1H,(H4,6,7,8,9,10,11)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = UYTPUPDQBNUYGX-UHFFFAOYSA-N
| CASNo = 73-40-5
| CASNo_Ref = {{cascite|correct|CAS}}
| RTECS = MF8260000
  }}
|Section2={{Chembox Properties
| Formula = C<sub>5</sub>H<sub>5</sub>N<sub>5</sub>O
| MolarMass = 151.13 g/mol
| Appearance = White amorphous solid.
| Density = 2.200 g/cm<sup>3</sup> (calculated)
| Solubility = Insoluble.
| MeltingPtC = 360
| MeltingPt_notes = decomposes
| BoilingPt = Sublimes
| pKa =3.3 (amide), 9.2 (secondary), 12.3 (primary)<ref>Dawson, R.M.C., et al., ''Data for Biochemical Research'', Oxford, Clarendon Press, 1959.</ref>
| Dipole =
  }}
|Section7={{Chembox Hazards
| MainHazards = Irritant
| NFPA-H = 1
| NFPA-F = 1
| NFPA-R =
| FlashPt = Non-flammable
  }}
|Section8={{Chembox Related
| OtherAnions =
| OtherCations =
| OtherCompounds = [[Cytosine]]; [[Adenine]]; [[Thymine]]; [[Uracil]]
  }}
}}
'''Guanine''' ({{IPAc-en|audio=En-us-guanine.ogg|ˈ|g|w|ɑː|n|iː|n}}) ([[nucleoside#List of nucleosides and corresponding nucleobases|symbol]] '''G''' or '''Gua''') is one of the four main [[nucleotide base]]s found in the [[nucleic acid]]s [[DNA]] and [[RNA]], the others being [[adenine]], [[cytosine]], and [[thymine]] ([[uracil]] in RNA). In [[DNA]], guanine is paired with cytosine. The guanine [[nucleoside]] is called [[guanosine]].

With the formula C<sub>5</sub>H<sub>5</sub>N<sub>5</sub>O, guanine is a derivative of [[purine]], consisting of a fused [[pyrimidine]]-[[imidazole]] ring system with conjugated double bonds. This unsaturated arrangement means the [[bicyclic molecule]] is planar.

==Properties==
Guanine, along with adenine and cytosine, is present in both DNA and RNA, whereas thymine is usually seen only in DNA, and uracil only in RNA. Guanine has multiple [[tautomer]]ic forms. For the [[imidazole]] ring, the proton can reside on either nitrogen.  For the pyrimidine ring, the ring N-H can center can reside on either of the ring nitrogens.  The latter tautomer does not apply to nucleoside or nucleotide versions of guanine.<ref>{{cite book|author=Saenger, W.|title=Principles of Nucleic Acid Structure|publisher=Springer Science & Business Media|year=1984|doi= 10.1007/978-1-4612-5190-3|page = 112}}</ref>

It binds to cytosine through three [[hydrogen bond]]s. In cytosine, the amino group acts as the hydrogen bond donor and the C-2 carbonyl and the N-3 amine as the hydrogen-bond acceptors. Guanine has the C-6 carbonyl group that acts as the hydrogen bond acceptor, while a group at N-1 and the amino group at C-2 act as the hydrogen bond donors.{{cn|date=February 2024}}

{{multiple image
| align=center
| total_width = 400
| image1=Cytonum2.svg
| caption1=[[Cytosine]]
| image2=Guannum2.svg
| caption2=Guanine
| footer=Cytosine and guanine with the direction of hydrogen bonding indicated (arrow points positive to negative charge)
}}

Guanine can be [[hydrolyzed]] with strong acid to [[glycine]], [[ammonia]], [[carbon dioxide]], and [[carbon monoxide]]. First, guanine gets [[Deamination|deaminated]] to become [[xanthine]].<ref>{{cite web |last=Angstadt |first=Carol N |title=Purines and pyrimidines |url=http://library.med.utah.edu/NetBiochem/pupyr/pp.htm |date=1997 |access-date=2024-11-20 |website=utah.edu}}</ref> Guanine oxidizes more readily than adenine, the other purine-derivative base in DNA. Its high melting point of 350&nbsp;°C reflects the intermolecular hydrogen bonding between the oxo and amino groups in the molecules in the crystal. Because of this intermolecular bonding, guanine is relatively insoluble in water, but it is soluble in dilute acids and bases.

==History==
The first isolation of guanine was reported in 1844 by the German chemist {{ill|Julius Bodo Unger|de|Bodo Unger (Chemiker)}} (1819–1885), who obtained it as a mineral formed from the excreta of sea birds, which is known as [[guano]] and which was used as a source of fertilizer; guanine was named in 1846.<ref>Guanine was first isolated in 1844 by Julius Bodo Unger (1819–1885), a student of [[Heinrich Gustav Magnus]]. See:
* [[Paul O. P. Ts'o]], ''Basic Principles in Nucleic Acid Chemistry'', vol. 1 (New York, New York: Academic Press, 1974), [https://books.google.com/books?id=oAKAbV7FHfgC&pg=PA7 page 7.]
* Magnus (1844) [https://books.google.com/books?id=nT49AAAAcAAJ&pg=PA395 "Ueber das Vorkommen von Xanthicoxyd im Guano"] (On the occurrence of xanthic oxide in guano), ''Annalen der Chemie und Pharmacie'', '''51''' : 395-397.
* B. Unger (1846) [https://books.google.com/books?id=7TU9AAAAcAAJ&pg=PA18 "Bemerkungen zu obiger Notiz"] (Comments on the above notice), ''Annalen der Chemie und Pharmacie'', '''58''' : 18-20. From page 20: ''" ... desshalb möchte ich den Namen ''Guanin'' vorschlagen, welcher an seine Herkunft erinnert."'' ( ... therefore I would like to suggest the name ''guanine'', which is reminiscent of its origin.)
* B. Unger (1846) [https://books.google.com/books?id=AjY9AAAAcAAJ&pg=PA58 "Das Guanin und seine Verbindungen"] (Guanine and its compounds), ''Annalen der Chemie und Pharmacie'', '''59''' : 58-68.</ref> Between 1882 and 1906, [[Hermann Emil Fischer|Emil Fischer]] determined the structure and also showed that [[uric acid]] can be converted to guanine.<ref>{{cite web |title = Emil Fischer - Biographical |url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1902/fischer-bio.html}}</ref>

==Synthesis==
Trace amounts of guanine form by the [[polymerization]] of [[ammonium cyanide]] ({{chem|NH|4|CN}}). Two experiments conducted by Levy et al. showed that heating 10&nbsp;mol·L<sup>−1</sup> {{chem|NH|4|CN}} at 80&nbsp;°C for 24 hours gave a yield of 0.0007%, while using 0.1&nbsp;mol·L<sup>−1</sup> {{chem|NH|4|CN}} frozen at −20&nbsp;°C for 25 years gave a 0.0035% yield. These results indicate guanine could arise in frozen regions of the primitive earth. In 1984, Yuasa reported a 0.00017% yield of guanine after the electrical discharge of {{chem|NH|3}}, {{chem|CH|4}}, {{chem|C|2|H|6}}, and 50&nbsp;mL of water, followed by a subsequent acid hydrolysis. However, it is unknown whether the presence of guanine was not simply a resultant contaminant of the reaction.<ref>{{cite journal | last = Levy | first = Matthew |author2=Stanley L. Miller |author3=John Oró | title = Production of Guanine from NH4CN Polymerizations | journal = Journal of Molecular Evolution | volume = 49 | issue = 2 | pages = 165–8 |date=August 1999 | doi = 10.1007/PL00006539 | pmid = 10441668| bibcode = 1999JMolE..49..165L | s2cid = 32194418 }} - quotes the Yuasa paper and cites the possibility of there being a contaminant in the reaction.</ref>

:10NH<sub>3</sub> + 2CH<sub>4</sub> + 4C<sub>2</sub>H<sub>6</sub> + 2H<sub>2</sub>O → 2C<sub>5</sub>H<sub>8</sub>N<sub>5</sub>O (guanine) + 25H<sub>2</sub>

A [[Fischer–Tropsch]] synthesis can also be used to form guanine, along with [[adenine]], [[uracil]], and [[thymine]]. Heating an equimolar gas mixture of CO, H<sub>2</sub>, and NH<sub>3</sub> to 700&nbsp;°C for 15 to 24 minutes, followed by quick cooling and then sustained reheating to 100 to 200&nbsp;°C for 16 to 44 hours with an alumina catalyst, yielded guanine and uracil:
:10CO + H<sub>2</sub> + 10NH<sub>3</sub> → 2C<sub>5</sub>H<sub>8</sub>N<sub>5</sub>O (guanine) + 8H<sub>2</sub>O

Another possible abiotic route was explored by quenching a 90% N<sub>2</sub>–10%CO–H<sub>2</sub>O gas mixture high-temperature plasma.<ref>{{cite journal | last = Miyakawa | first = S |author2=Murasawa, K. |author3=Kobayashi, K. |author4=Sawaoka, AB. | title = Abiotic synthesis of guanine with high-temperature plasma | journal = Orig Life Evol Biosph | volume = 30 | issue = 6 | pages = 557–66 |date=December 2000 | doi = 10.1023/A:1026587607264 | pmid = 11196576| bibcode = 2000OLEB...30..557M | s2cid = 25417484 }}</ref>

[[Traube purine synthesis|Traube's synthesis]] involves heating [[4-Hydroxy-2,4,5-triaminopyrimidine|4-hydroxy-2,4,5-triaminopyrimidine]] with [[formic acid]] for several hours.<ref>{{cite journal|title=Über Ortho-diamino-pyrimidine und ihre Überführung in Purine|trans-title= o-Diaminopyrimidines and their transformation into purines|author=Traube, Wilhelm; Schottlander, Friedrich; Goslich, Carl; Peter, Robert; Meyer, F. A.; Schlüter, Heinrich; Steinbach, Wilhelm; Bredow, Karl|journal=Justus Liebigs Annalen der Chemie |year=1923|volume=432|page=266-96|doi=10.1002/jlac.19234320111}}</ref>
[[Image:TraubePurineSynthesis.svg|Traube purine synthesis]]

==Biosynthesis==
Guanine is not synthesized [[de novo synthesis|de novo]].{{clarification needed|date=March 2022}} Instead, it is split from the more complex molecule [[guanosine]] by the enzyme [[guanosine phosphorylase]]:

:guanosine + phosphate <math>\rightleftharpoons</math> guanine + alpha-D-ribose 1-phosphate
Guanine can be synthesized de novo, with the rate-limiting enzyme of [[Inosine-5′-monophosphate dehydrogenase|inosine monophosphate dehydrogenase]].

==Other occurrences and biological uses==
The word guanine derives from the Spanish loanword {{lang|es|guano}} ('bird/bat droppings'), which itself is from the [[Quechua language|Quechua]] word {{lang|qu|wanu}}, meaning 'dung'. As the [[Oxford English Dictionary]] notes, guanine is "A white amorphous substance obtained abundantly from guano, forming a constituent of the excrement of birds".<ref>OED. "guanine" and also "guano".</ref>

In 1656 in Paris, a Mr. Jaquin extracted from the scales of the fish [[Common bleak|''Alburnus alburnus'']] so-called "pearl essence",<ref>Johann Rudolf von Wagner, Ferdinand Fischer, and L. Gautier, ''Traité de chimie industrielle'' (Treatise on industrial chemistry), 4th ed., (Paris, France:  Masson & Co., 1903), vol. 2, [https://books.google.com/books?id=K2mhGDwiSJsC&pg=PA64 pp. 64–65.]</ref> which is crystalline guanine.<ref>In 1861 the French chemist [[Charles-Louis Barreswil]] (1817–1870) found that "pearl essence" was guanine.  See:  Barreswil (1861) [http://gallica.bnf.fr/ark:/12148/bpt6k3010v/f246.item.zoom "Sur le blanc d'ablette qui sert à la fabrication des perles fausses"] (On the white of ablette that's used in making imitation pearls), ''Comptes rendus'', '''53''' :  246.</ref> In the cosmetics industry, crystalline guanine is used as an additive to various products (e.g., shampoos), where it provides a pearly [[iridescence|iridescent]] effect. It is also used in metallic paints and simulated pearls and plastics. It provides shimmering luster to eye shadow and [[nail polish]]. Facial treatments using the droppings, or guano, from Japanese nightingales have been used in Japan and elsewhere, because the guanine in the [[Uguisu no fun|dropping]]s makes the skin look paler.<ref>{{cite web |title=Geisha facial, the 'latest beauty secret' of Victoria Beckham, brought to the masses |last=Whitworth |first=Melissa |date=2008-10-16 |access-date=2008-11-20 |url=https://www.telegraph.co.uk/fashion/beauty/3365670/Geisha-facial%2C-the-%27latest-beauty-secret%27-of-Victoria-Beckham%2C-brought-to-the-masses.html |archive-url=https://web.archive.org/web/20081205010654/http://www.telegraph.co.uk/fashion/beauty/3365670/Geisha-facial%2C-the-%27latest-beauty-secret%27-of-Victoria-Beckham%2C-brought-to-the-masses.html |url-status=dead |archive-date=2008-12-05 |publisher=Telegraph |work=Lifestyle}}</ref> Guanine crystals are rhombic platelets composed of multiple transparent layers, but they have a high [[Refractive index|index of refraction]] that partially reflects and transmits light from layer to layer, thus producing a pearly luster. It can be applied by spray, painting, or dipping. It may irritate the eyes. Its alternatives are [[mica]], faux pearl (from ground shells),<ref>{{cite journal |title=How Pearls are Made...Faux, Fake, Imitation, Simulated or Man-made |url=http://www.karipearls.com/how-pearls-are-made.html}}</ref> and [[aluminium]] and [[bronze]] particles.

Guanine has a very wide variety of biological uses that include a range of functions ranging in both complexity and versatility. These include camouflage, display, and vision among other purposes.<ref name=":0" />

Spiders, scorpions, and some amphibians convert ammonia, as a product of protein metabolism in the cells, to guanine, as it can be excreted with minimal water loss.<ref name=":0">{{Cite journal |date=2017 |title=Light manipulation by guanine crystals in organisms: biogenic scatterers, mirrors, multilayer reflectors and photonic crystals |journal=Advanced Functional Materials |volume=27 |issue=6 |page=1603514 |doi=10.1002/adfm.201603514 |last1=Gur |first1=Dvir |last2=Palmer |first2=Benjamin A. |last3=Weiner |first3=Steve |last4=Addadi |first4=Lia |s2cid=136383728 }}</ref>

Guanine is also found in specialized skin cells of fish called [[iridocyte]]s (e.g., the [[sturgeon]]),<ref name="fox"/><ref name=":0" /> as well as being present in the reflective deposits of the eyes of [[deep-sea fish]] and some [[reptile]]s, such as [[crocodile]]s and [[chameleon]]s.<ref name="fox">{{cite book |last=Fox |first=D.L. |year=1979 |title=Biochromy, natural coloration of living things |publisher=University of California Press |isbn=978-0-520-03699-4}}</ref>

On 8 August 2011, a report, based on [[NASA]] studies with [[meteorites]] found on Earth, was published suggesting building blocks of DNA and RNA (guanine, [[adenine]] and related [[organic molecules]]) may have been formed extra-terrestrially in outer space.<ref name="Callahan">{{cite journal |last1=Callahan |last2=Smith |first2=K.E. |last3=Cleaves |first3=H.J. |last4=Ruzica |first4=J. |last5=Stern |first5=J.C. |last6=Glavin |first6=D.P. |last7=House |first7=C.H. |last8=Dworkin |first8=J.P. |date=11 August 2011 |title=Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases |publisher=[[PNAS]] |doi=10.1073/pnas.1106493108 |pmid=21836052 |pmc=3161613 |volume=108 |issue=34 |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |pages=13995–8 |bibcode=2011PNAS..10813995C |doi-access=free }}</ref><ref name="Steigerwald">{{cite web |last=Steigerwald |first=John |title=NASA Researchers: DNA Building Blocks Can Be Made in Space |url=http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |publisher=[[NASA]] |date=8 August 2011 |access-date=2011-08-10 |archive-date=2015-06-23 |archive-url=https://web.archive.org/web/20150623004556/http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |url-status=dead }}</ref><ref name="DNA">{{cite web |title=DNA Building Blocks Can Be Made in Space, NASA Evidence Suggests |url=https://www.sciencedaily.com/releases/2011/08/110808220659.htm |date=9 August 2011 |website=[[ScienceDaily]] |access-date=2011-08-09 }}</ref>

==See also==
* [[Cytosine]]
* [[Guanine deaminase]]

==References==
{{Reflist}}

==External links==
{{Commons category|Guanine}}
* [http://gmd.mpimp-golm.mpg.de/Spectrums/d84fcceb-5982-470a-a0d5-03450fb8aa47.aspx Guanine MS Spectrum]
* [http://www.chemicalland21.com/lifescience/phar/GUANINE.htm Guanine] at chemicalland21.com

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

[[Category:Nucleobases]]
[[Category:Purines]]
[[Category:Cosmetics chemicals]]
[[Category:Organic minerals]]