Guanine

Guanine
IUPAC name	2-amino-1H-purin-6(9H)-one
Other names	2-amino-6-oxo-purine, 2-aminohypoxanthine, Guanine
Identifiers
CAS number	73-40-5
RTECS number	MF8260000
SMILES	NC1=Nc2[nH]cnc2C(=O)N1
Properties
Molecular formula	C5H5N5O
Molar mass	151.1261 g/mol
Appearance	White amorphous solid.
Density	, solid.
Melting point	360°C (633.15 K) deco.
Boiling point	Sublimes.
Solubility in water	Insoluble.
Dipole moment	? D
Hazards
Main hazards	Irritant.
NFPA 704	1 1 0
Flash point	Non-flammable.
Related Compounds
Related compounds	Cytosine; Adenine; Thymine; Uracil
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

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Overview

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.

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.

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 later, 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 an 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 1656 in Paris, François Jaquin (a rosary maker) extracted from scales of some fishes the so called pearl essence, crystalline guanine forming G-quadruplexes: in cosmetic industry, crystalline guanine is used as an additive to various products (e.g., shampoos), where it provides the pearly iridescent effect. It is also used in metallic paints and simulated pearls and plastics. It provides shimmering lustre to eye shadow and nail polish. Guanine crystals are rhombic platelets composed of multiple, transparent layers but they have a high 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 eyes. Its alternatives are mica, synthetic pearl, and aluminium and bronze particles.

See also

• Guanine deaminase

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

• Computational Chemistry Wiki
• Good Guanine reference

<tr bgcolor="#ccccff"><td colspan="3" align="center">Major families of biochemicals</td></tr><tr><td colspan="3" style="text-align: center;">Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides</td></tr><tr bgcolor="pink"><td style="white-space: nowrap; width: 10%; color: pink;">Analogues of nucleic acids:</td><td align="center">Types of Nucleic Acids</td><td style="white-space: nowrap; width: 10%; color: pink;">Analogues of nucleic acids:</td></tr> Cost Effectiveness of Guanine

| group5 = Clinical Trials Involving Guanine | list5 = Ongoing Trials on Guanine at Clinical Trials.gov • Trial results on Guanine • Clinical Trials on Guanine at Google

| group6 = Guidelines / Policies / Government Resources (FDA/CDC) Regarding Guanine | list6 = US National Guidelines Clearinghouse on Guanine • NICE Guidance on Guanine • NHS PRODIGY Guidance • FDA on Guanine • CDC on Guanine

| group7 = Textbook Information on Guanine | list7 = Books and Textbook Information on Guanine

| group8 = Pharmacology Resources on Guanine | list8 = AND (Dose)}} Dosing of Guanine • AND (drug interactions)}} Drug interactions with Guanine • AND (side effects)}} Side effects of Guanine • AND (Allergy)}} Allergic reactions to Guanine • AND (overdose)}} Overdose information on Guanine • AND (carcinogenicity)}} Carcinogenicity information on Guanine • AND (pregnancy)}} Guanine in pregnancy • AND (pharmacokinetics)}} Pharmacokinetics of Guanine •

| group9 = Genetics, Pharmacogenomics, and Proteinomics of Guanine | list9 = AND (pharmacogenomics)}} Genetics of Guanine • AND (pharmacogenomics)}} Pharmacogenomics of Guanine • AND (proteomics)}} Proteomics of Guanine

| group10 = Newstories on Guanine | list10 = Guanine in the news • Be alerted to news on Guanine • News trends on Guanine</small>

| group11 = Commentary on Guanine | list11 = Blogs on Guanine

| group12 = Patient Resources on Guanine | list12 = Patient resources on Guanine • Discussion groups on Guanine • Patient Handouts on Guanine • Directions to Hospitals Treating Guanine • Risk calculators and risk factors for Guanine

| group13 = Healthcare Provider Resources on Guanine | list13 = Symptoms of Guanine • Causes & Risk Factors for Guanine • Diagnostic studies for Guanine • Treatment of Guanine

| group14 = Continuing Medical Education (CME) Programs on Guanine | list14 = CME Programs on Guanine

| group15 = International Resources on Guanine | list15 = Guanine en Espanol • Guanine en Francais

| group16 = Business Resources on Guanine | list16 = Guanine in the Marketplace • Patents on Guanine

| group17 = Informatics Resources on Guanine | list17 = List of terms related to Guanine

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