Jump to: navigation, search
IUPAC name 2-amino-1H-purin-6(9H)-one
Other names 2-amino-6-oxo-purine,
CAS number 73-40-5
RTECS number MF8260000
SMILES NC1=Nc2[nH]cnc2C(=O)N1
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


Solubility in water Insoluble.
Dipole moment  ? D
Main hazards Irritant.
NFPA 704

NFPA 704.svg

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

WikiDoc Resources for Guanine


Most recent articles on Guanine

Most cited articles on Guanine

Review articles on Guanine

Articles on Guanine in N Eng J Med, Lancet, BMJ


Powerpoint slides on Guanine

Images of Guanine

Photos of Guanine

Podcasts & MP3s on Guanine

Videos on Guanine

Evidence Based Medicine

Cochrane Collaboration on Guanine

Bandolier on Guanine

TRIP on Guanine

Clinical Trials

Ongoing Trials on Guanine at Clinical

Trial results on Guanine

Clinical Trials on Guanine at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Guanine

NICE Guidance on Guanine


FDA on Guanine

CDC on Guanine


Books on Guanine


Guanine in the news

Be alerted to news on Guanine

News trends on Guanine


Blogs on Guanine


Definitions of Guanine

Patient Resources / Community

Patient resources on Guanine

Discussion groups on Guanine

Patient Handouts on Guanine

Directions to Hospitals Treating Guanine

Risk calculators and risk factors for Guanine

Healthcare Provider Resources

Symptoms of Guanine

Causes & Risk Factors for Guanine

Diagnostic studies for Guanine

Treatment of Guanine

Continuing Medical Education (CME)

CME Programs on Guanine


Guanine en Espanol

Guanine en Francais


Guanine in the Marketplace

Patents on Guanine

Experimental / Informatics

List of terms related to Guanine


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.


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


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. <br\> 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. <br\> 3. Lister, J.H. "Part II Purines." The Chemistry of Heterocyclic Compounds. Wiley-Interscience (New York). 1971.

External links

<tr bgcolor="#ccccff"><td colspan="3" align="center">
v  d  e
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>
Nucleobases: Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides: Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine
Nucleotides: monophosphates (AMP, GMP, UMP, CMP) | diphosphates (ADP, GDP, UDP, CDP) | triphosphates (ATP, GTP, UTP, CTP) | cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides: monophosphates (dAMP, dGMP, TMP, dCMP) | diphosphates (dADP, dGDP, TDP, dCDP) | triphosphates (dATP, dGTP, TTP, dCTP)
Ribonucleic acids: RNA | mRNA | tRNA | rRNA | gRNA | miRNA | ncRNA | piRNA | shRNA | siRNA | snRNA | snoRNA
Deoxyribonucleic acids: DNA | mtDNA | cDNA
Nucleic acid analogues: GNA | LNA | PNA | TNA | morpholino
Cloning vectors: plasmid | cosmid | fosmid | phagemid | BAC | YAC | HAC