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Adenine (Template:IPAc-en, Template:IPAc-en) (symbol A or Ade) is a purine nucleotide base that is found in DNA, RNA, and ATP.<ref name="Myers">Template:Cite book</ref> Usually a white crystalline subtance.<ref name="Myers" /> The shape of adenine is complementary and pairs to either thymine in DNA or uracil in RNA.<ref name="Myers" /> In cells adenine, as an independent molecule, is rare. It is almost always covalently bound to become a part of a larger biomolecule.
Adenine has a central role in cellular respiration. It is part of adenosine triphosphate which provides the energy that drives and supports most activities in living cells, such as protein synthesis, chemical synthesis, muscle contraction, and nerve impulse propagation.<ref>Template:Cite journal</ref> In respiration it also participates as part of the cofactors nicotinamide adenine dinucleotide, flavin adenine dinucleotide, and Coenzyme A.
It is also part of adenosine, adenosine monophosphate, cyclic adenosine monophosphate, adenosine diphosphate, and S-adenosylmethionine.
StructureEdit
Adenine forms several tautomers, compounds that can be rapidly interconverted and are often considered equivalent. However, in isolated conditions, i.e. in an inert gas matrix and in the gas phase, mainly the 9H-adenine tautomer is found.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
BiosynthesisEdit
Purine metabolism involves the formation of adenine and guanine. Both adenine and guanine are derived from the nucleotide inosine monophosphate (IMP), which in turn is synthesized from a pre-existing ribose phosphate through a complex pathway using atoms from the amino acids glycine, glutamine, and aspartic acid, as well as the coenzyme tetrahydrofolate.
Patented August 20, 1968, the current recognized method of industrial-scale production of adenine involves heating formamide under 120 °C.<ref>Template:Cite patent</ref>
FunctionEdit
Adenine is one of the two purine nucleobases (the other being guanine) used in forming nucleotides of the nucleic acids. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. In RNA, which is used for protein synthesis, adenine binds to uracil.
| File:Base pair AT.svg | File:Base pair AU.svg | File:Base pair AD.svg | File:Base pair APsi.svg |
| A-T-Base-pair (DNA) | A-U-Base-pair (RNA) | A-D-Base-pair (RNA) | A-Ψ-Base-pair (RNA) |
Adenine forms adenosine, a nucleoside, when attached to ribose, and deoxyadenosine when attached to deoxyribose.<ref name="Myers" /> It forms adenosine triphosphate (ATP), a nucleoside triphosphate, when three phosphate groups are added to adenosine. Adenosine triphosphate is used in cellular metabolism as one of the basic methods of transferring chemical energy between chemical reactions.<ref name="Myers" /> ATP is thus a derivative of adenine, adenosine, cyclic adenosine monophosphate, and adenosine diphosphate.
File:Adenosin.svg File:Desoxyadenosin.svg Adenosine, A Deoxyadenosine, dA
HistoryEdit
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In older literature, adenine was sometimes called Vitamin B4, but is no longer considered a vitamin.<ref>Template:Cite journal</ref><ref name="Myers" /> Due to it being synthesized by the body and not essential to be obtained by diet, it does not meet the definition of vitamin and is no longer part of the Vitamin B complex. However, two B vitamins, niacin and riboflavin, bind with adenine to form the essential cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD), respectively. Hermann Emil Fischer was one of the early scientists to study adenine.
It was named in 1885 by Albrecht Kossel after Greek ἀδήν aden "gland", in reference to the pancreas, from which Kossel's sample had been extracted.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Adenine can be prepared from ammonia and hydrogen cyanide (HCN) in aqueous solution,<ref>Template:Cite journal</ref> a process that has implications for the origin of life on Earth.<ref>Template:Cite journal</ref>
On August 8, 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting building blocks of DNA and RNA (adenine, guanine and related organic molecules) may have been formed extraterrestrially in outer space.<ref name="Callahan">Template:Cite journal</ref><ref name="Steigerwald">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="DNA">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2011, physicists reported that adenine has an "unexpectedly variable range of ionization energies along its reaction pathways" which suggested that "understanding experimental data on how adenine survives exposure to UV light is much more complicated than previously thought"; these findings have implications for spectroscopic measurements of heterocyclic compounds, according to one report.<ref name=twsA35>{{#invoke:citation/CS1|citation |CitationClass=web }}
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ReferencesEdit
External linksEdit
Template:Nucleobases, nucleosides, and nucleotides Template:Vitamin