Purine
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226031237
2008-07-16T14:55:14Z
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/* Functions */
{{Chembox new
|ImageFile=Purine chemical structure.png
|ImageSize= 345px
|ImageFile2=
|IUPACName=7H-purine
|OtherNames=
|Section1= {{Chembox Identifiers
| CASNo=120-73-0
| PubChem=1044
| SMILES=C1=C2C(=NC=N1)N=CN2
| MeSHName=Purine
}}
|Section2= {{Chembox Properties
| Formula=C<sub>5</sub>H<sub>4</sub>N<sub>4</sub>
| MolarMass=120.112
| Appearance=
| Density=
| MeltingPt=214 °C
| BoilingPt=
| Solubility=
}}
|Section3= {{Chembox Hazards
| MainHazards=
| FlashPt=
| Autoignition=
}}
}}
'''Purine''' ('''1''') is a [[heterocyclic compound|heterocyclic]] [[aromatic]] [[organic compound]], consisting of a [[pyrimidine]] ring fused to an [[imidazole]] ring. Purines and pyrimidines make up the two groups of [[nitrogenous bases]]. These bases make up a crucial part of both deoxyribonucleotides and ribonucleotides, and the basis for the universal genetic code.
The general term '''purines''' also refers to substituted purines and their [[tautomer]]s.
The purine is the most widely distributed nitrogen-containing [[heterocycle]] in nature.<ref>Rosemeyer, H. ''Chemistry & Biodiversity'' '''2004''', ''1'', 361.</ref>
==Notable purines==
The quantity of naturally occurring purines produced on earth is enormous, as 50 % of the bases in [[nucleic acid]]s, [[adenine]] ('''2''') and [[guanine]] ('''3'''), are purines. In [[DNA]], these bases form [[hydrogen bond]]s with their [[complementarity (molecular biology)|complementary]] [[pyrimidine]]s [[thymine]] and [[cytosine]]. This is called complementary base pairing. In [[RNA]], the complement of adenine is [[uracil]] (U) instead of thymine.
Other notable purines are [[hypoxanthine]] ('''4'''), [[xanthine]] ('''5'''), [[theobromine]] ('''6'''), [[caffeine]] ('''7'''), [[uric acid]] ('''8''') and [[isoguanine]] ('''9''').
[[Image:purines.gif]]
==Functions==
Aside from DNA and RNA, purines are biochemically significant components in a number of other important biomolecules, such as [[Adenosine triphosphate|ATP]], [[Guanosine triphosphate|GTP]], [[cyclic AMP]], [[NADH]], and [[coenzyme A]]. Purine ('''1''') itself, has not been found in nature, but it can be produced by [[organic synthesis]].
They may also function directly as [[neurotransmitters]], acting upon [[purinergic receptors]]. Adenosine activates [[adenosine receptor]]s.
== History ==
The name 'purine' (''purum uricum'') was coined by the [[Germany|German]] [[chemist]] [[Emil Fischer]] in [[1884]]. He synthesized it for the first time in [[1899]].<ref>Fischer, E. ''Berichte der Deutschen Chemischen Gesellschaft'' '''1899''', ''32'', 2550.</ref> The starting material for the reaction sequence was uric acid ('''8'''), which had been isolated from kidney stones by Scheele in 1776.<ref>Scheele, V. Q. Examen Chemicum Calculi Urinari, ''Opuscula'', '''1776''', ''2'', 73.</ref> Uric acid (8) was reacted with PCl<sub>5</sub> to give 2,6,8-trichloropurine ('''10'''), which was converted with HI and [[Phosphonium salt|PH<sub>4</sub>I]] to give 2,6-diiodopurine ('''11'''). This latter product was reduced to purine ('''1''') using zinc-dust.
[[Image:FischerPurineSynthesis.gif]]
== Metabolism ==<!-- This section is linked from [[Metabolism]] -->
{{main|Purine metabolism}}
Many organisms have [[metabolic pathway]]s to synthesize and break down purines.
Purines are biologically synthesized as [[nucleoside]]s (bases attached to [[ribose]]).
== Food Sources==
Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney. Plant based diet is generally low in purines [http://www.dietaryfiberfood.com/purine-food.php].
Examples of high purine sources include: sweetbreads, anchovies, sardines, liver, beef, kidneys, brains, [[Meat extract|meat extracts]], herring, mackerel, scallops, game meats, and gravy.
A moderate amount of purine is also contained in beef, pork, poultry, fish and seafood, asparagus, cauliflower, spinach, mushrooms, green peas, lentils, dried peas, beans, oatmeal, wheat bran and wheat germ.<ref>[http://www.healthcastle.com/gout.shtml Gout Diet: Limit High Purine Foods<!-- Bot generated title -->]</ref>
Moderate intake of purine-containing food is not associated with an increased risk of [[gout]].<ref>[http://content.nejm.org/cgi/content/abstract/350/11/1093 NEJM - Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men<!-- Bot generated title -->]</ref>
==Laboratory synthesis ==
In addition to [[in vivo]] synthesis of purines in [[purine metabolism]], purine can also be created artificially.
Purine ('''1''') is obtained in good yield when formamide is heated in an open vessel at 170 <sup>o</sup>C for 28 hours.<ref name="Yamada">Yamada, H.; Okamoto, T. ''Chemical & Pharmaceutical Bulletin'', '''1972''', ''20'', 623.</ref>
[[Image:Purinesynthesis.gif]]
Procedure:<ref name="Yamada"> </ref>
Formamide (45 gram) was heated in an open vessel with a condenser for 28 hours in an oil bath at 170-190 <sup>o</sup>C. After removing excess formamide (32.1 gram) by vacuum distillation, the residue was refluxed with methanol. The methanol solvent was filtered, the solvent removed from the filtrate by vacuum distillation, and almost pure purine obtained; yield 4.93 gram (71 % yield from formamide consumed). Crystallization from acetone afforded purine as colorless crystals; melting point 218 <sup>o</sup>C.
Oro, Orgel and co-workers have shown that four molecules of HCN tetramerize to form diaminomaleodinitrile ('''12'''), which can be converted into almost all important natural occurring purines.<ref>Sanchez, R. A.; Ferris, J. P.; Orgel, L. E. ''Journal of Molecular Biology'', '''1967''', ''30'', 223.</ref><ref>Ferris, J. P.; Orgel, L. E. ''Journal of the American Chemical Society'', '''1966''', ''88'', 1074.</ref><ref>Ferris, J. P.; Kuder, J. E.; Catalano, O. W. ''Science'', '''1969''', ''166'', 765.</ref><ref>Oro, J.; Kamat, J. S. ''Nature'', '''1961''', ''190'', 442.</ref><ref>Houben-Weyl, Vol . E5, p. 1547</ref>
[[Image:basicpurines.gif]]
The '''Traube purine synthesis''' (1900) is a classic reaction (named after [[Wilhelm Traube]]) between an [[amine]] substutited [[pyrimidine]] and [[formic acid]] <ref>''Organic Syntheses Based on Name Reactions'', Alfred Hassner, C. Stumer ISBN 008043259X 2002</ref>
[[Image:TraubePurineSynthesis.svg|Traube purine synthesis]]
== References ==
<references/>
== See also ==
* [[Simple aromatic ring]]s
* [[Pyrimidine]]
== External links ==
*[http://www.compchemwiki.org/index.php?title=Purine Computational Chemistry Wiki]
*[http://www.dietaryfiberfood.com/purine-food.php Purine Content in Food]
{{Nucleobases, nucleosides, and nucleotides}}
[[Category:Purines]]
[[Category:Amines]]
[[Category:Nitrogen heterocycles]]
[[Category:Aromatic compounds]]
[[Category:Heterocyclic compounds]]
[[Category:Simple aromatic rings]]
[[Category:Aromatic bases]]
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