Adenine

Adenine
Names
IUPAC name
9H-purin-6-amine
Other names
6-aminopurine
Identifiers
73-24-5 Y
ChEBI CHEBI:16708 Y
ChEMBL ChEMBL226345 Y
ChemSpider 185 Y
DrugBank DB00173 Y
EC Number 200-796-1
4788
Jmol 3D model Interactive image
Interactive image
KEGG D00034 Y
PubChem 190
RTECS number AU6125000
UNII JAC85A2161 Y
Properties
C5H5N5
Molar mass 135.13 g/mol
Appearance white to light yellow, crystalline
Density 1.6 g/cm3 (calculated)
Melting point 360 to 365 °C (680 to 689 °F; 633 to 638 K) decomposes
0.103 g/100 mL
Solubility negligible in ethanol
Acidity (pKa) 4.15 (secondary), 9.80 (primary)
Thermochemistry
147.0 J/(K·mol)
Std enthalpy of
formation (ΔfHo298)
96.9 kJ/mol
Hazards
Safety data sheet MSDS
Lethal dose or concentration (LD, LC):
LD50 (Median dose)
227 mg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Adenine /ˈædnn/ (A, Ade) is a nucleobase (a purine derivative). Its derivatives have a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). It also has functions in protein synthesis and as a chemical component of DNA and RNA. The shape of adenine is complementary to either thymine in DNA or uracil in RNA.

The image right shows pure adenine, as an independent molecule. When connected into DNA, a covalent bond is formed between deoxyribose sugar and the bottom left nitrogen, so removing the hydrogen. The remaining structure is called an adenine residue, as part of a larger molecule. Adenosine is adenine reacted with ribose as used in RNA and ATP; deoxyadenosine adenine attached to deoxyribose, as is used to form DNA.

    Structure

    Adenine structure, with standard numbering of positions in red.

    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.

    Biosynthesis

    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.

    Function

    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.

    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. 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.

    Adenosine, A Deoxyadenosine, dA

    History

    Adenine on Crick and Watson’s DNA molecular model, 1953. The picture is shown upside down compared to most modern drawings of adenine, such as those used in this article.

    In older literature, adenine was sometimes called Vitamin B4. It is no longer considered a true vitamin or 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, in reference to the pancreas (a specific gland - in Greek, "aden") from which Kossel's sample had been extracted.

    Experiments performed in 1961 by Joan Oró have shown that a large quantity of adenine can be synthesized from the polymerization of ammonia with five hydrogen cyanide (HCN) molecules in aqueous solution; whether this has implications for the origin of life on Earth is under debate.

    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. 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.

    References

    External links

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