Guanine

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Guanine

General
Systematic name	2-amino-1H-purin-6(9H)-one
Other names	2-amino-6-oxo-purine, 2-aminohypoxanthine, Guanine
Molecular formula	C₅H₅N₅O
SMILES	NC(NC1=O)=NC2=C1N=CN2
Molar mass	151.13 g/mol
Appearance	White amorphous solid.
CAS number
Properties
Density and phase	? g/cm³, solid.
Solubility in water	Insoluable.
Melting point	360°C (633.15 K) deco.
Boiling point	Sublimes.
Structure
Crystal structure	?
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	Irritant.
NFPA 704
Flash point	Non-flammable.
R/S statement	R: R36, R37, R38. S: R24/25, R26, R36.
RTECS number	MF8260000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	?
Other cations	?
Related ?	?
Related compounds	Cytosine, Adenine, Thymine, Uracil
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) [Chemical infoboxInfobox disclaimer and references]

Guanine is one of the five main nucleobases found in the nucleic acids DNA and RNA; the others being adenine, cytosine, thymine, and uracil. With the formula C₅H₅N₅O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with conjugated double bonds. Being unsaturated, the bicyclic molecule is planar. The guanine nucleoside is called guanosine.

Contents

1 Basic principles
2 Isolation, background, & some chemistry
3 Syntheses
4 Other Uses
5 References
6 External links

Basic principles

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 two tautomeric forms, the keto form and enol form. It binds to cytosine through three hydrogen bonds. In cytosine, the amino group acts as the hydrogen donor and the C-2 carbonyl and the N-3 amine as the hydrogen-bond acceptors. Guanine has a group at C-6 that acts as the hydrogen acceptor, while the group at N-1 and the amino group at C-2 acts as the hydrogen donors. over

Isolation, background, & some chemistry

The first isolation of guanine was reported in 1844 from the excreta of sea birds, known as guano, which was used as a source of fertilizer. About fifty years Fischer determined the structure and also showed that uric acid can be converted to guanine. The first complete synthesis was done by Traube and remains among the best large-scale preparations.

Guanine can be hydrolyzed with strong acid to glycine, ammonia, carbon dioxide, and carbon monoxide at 180°C. Guanine oxidizes more readily than adenine, the other purine-derivative base in DNA and RNA. Its high melting point of 350°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, although it is soluble in dilute acids and bases.

Syntheses

Trace amounts of guanine form by the polymerization of ammonium cyanide (NH₄CN). Two experiments conducted by Levy et al., showed that heating 10 M NH₄CN at 80°C for 24 hours gave a yield of 0.0007% while using 0.1 M NH₄CN frozen at -20°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 NH₃, CH₄, C₂H₆, and 50 mL of water, followed by a subsequent acid hydrolysis. However, it is unknown if the presence of guanine was not simply resulted from a contaminant of the reaction.

5NH₃ + CH₄ + 2C₂H₆ + H₂O → C₅H₈N₅O (guanine) + (25/2)H₂

A Fischer-Tropsch synthesis can also be used to form guanine, along with adenine, uracil and thymine. Heating a equimolar gas mixture of CO, H₂, and NH₃ to 700 °C for 0.24 to 0.4 hours, followed by quick cooling and then sustainted reheating to 100-200°C for 16-44 hours with an alumina catalyst yielded guanine and uracil:

5CO + (1/2)H₂ + 5NH₃ → C₅H₈N₅O (guanine) + 4H₂O

Traube's synthesis involves heating 2,4,5-triamino-1,6-dihydro-6-oxypyrimidine (as the sulphate) with formic acid for several hours.

Other Uses

In cosmetic industry, crystalline guanine is used as an additive to various products (e.g., shampoos), where it provides the pearly iridescent effect. It provides shimmering lustre to eye shadow and nail polish.It may irritate eyes. Its alternatives are mica, synthetic pearl, and aluminium and bronze particles.

References

1. Miyakawa, S., Murasawa, K., Kobayashi, K., Sawaoka, AB. "Abiotic synthesis of guanine with high-temperature plasma." Orig Life Evol Biosph. 30(6): 557-66, Dec. 2000. 2. Horton, H.R., Moran, L.A., Ochs, R.S., Rawn, J.D., Scrimgeour, K.G. "Principles of Biochemistry." Prentice Hall (New Jersey). 3rd Edition, 2002. 3. Lister, J.H. "Part II Purines." The Chemistry of Heterocyclic Compounds. Wiley-Interscience (New York). 1971.

External links

For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].

Nucleic acids [http://encycl.opentopia.com/ edit]
Nucleobases: Adenine \| Thymine \| Uracil \| Guanine \| Cytosine \| Purine \| Pyrimidine
Nucleosides: Adenosine \| Uridine \| Guanosine \| Cytidine \| Deoxyadenosine \| Thymidine \| Deoxyguanosine \| Deoxycytidine
Nucleotides: AMP \| UMP \| GMP \| CMP \| ADP \| UDP \| GDP \| CDP \| ATP \| UTP \| GTP \| CTP \| cAMP \| cGMP
Deoxynucleotides: dAMP \| dTMP \| dGMP \| dCMP \| dADP \| dTDP \| dGDP \| dCDP \| dATP \| dTTP \| dGTP \| dCTP
Nucleic acids: DNA \| mtDNA \| cDNA \| GNA \| RNA \| mRNA \| tRNA \| rRNA \| ncRNA \| sgRNA \| shRNA \| siRNA \| snRNA \| miRNA \| snoRNA \| LNA \| PNA \| TNA \| Oligonucleotide

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