Cytosine

Cytosine

Names
IUPAC name 4-aminopyrimidin-2(1H)-one
Other names 4-amino-1H-pyrimidine-2-one
Identifiers
CAS Registry Number	Y
ChEBI	Y
ChEMBL	Y
ChemSpider	Y
InChI InChI=1S/C4H5N3O/c5-3-1-2-6-4(8)7-3/h1-2H,(H3,5,6,7,8) Y Key: OPTASPLRGRRNAP-UHFFFAOYSA-N Y InChI=1/C4H5N3O/c5-3-1-2-6-4(8)7-3/h1-2H,(H3,5,6,7,8) Key: OPTASPLRGRRNAP-UHFFFAOYAY
Jmol-3D images	Image
KEGG	Y
MeSH
PubChem
SMILES c1cnc(=O)[nH]c1N
UNII	Y
Properties
Chemical formula	C4H5N3O
Molar mass	111.10 g/mol
Density	1.55 g/cm3 (calculated)
Melting point	320 to 325 °C (608 to 617 °F; 593 to 598 K) (decomposes)
Acidity (pKa)	4.45 (secondary), 12.2 (primary)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (: Y/N?)

Cytosine (C) is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine. In Watson-Crick base pairing, it forms three hydrogen bonds with guanine.

History

Cytosine was discovered and named by Albrecht Kossel and Albert Neumann in 1894 when it was hydrolyzed from calf thymus tissues.^[2][3] A structure was proposed in 1903, and was synthesized (and thus confirmed) in the laboratory in the same year.

Cytosine recently found use in quantum computation. The first time any quantum mechanical properties were harnessed to process information took place on August 1 in 1998 when researchers at Oxford implemented David Deutsch's algorithm on a two qubit nuclear magnetic resonance quantum computer (NMRQC) based on cytosine.^[4]

In March 2015, NASA scientists reported that, for the first time, complex life, including uracil, cytosine and thymine, have been formed in the laboratory under outer space conditions, using starting chemicals, such as pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), the most carbon-rich chemical found in the Universe, may have been formed in red giants or in interstellar dust and gas clouds, according to the scientists.^[5]

Chemical reactions

Cytosine with numbered components. Methylation occurs on carbon nr 5.

Cytosine can be found as part of DNA, as part of RNA, or as a part of a nucleotide. As cytidine triphosphate (CTP), it can act as a co-factor to enzymes, and can transfer a phosphate to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP).

In DNA and RNA, cytosine is paired with guanine. However, it is inherently unstable, and can change into uracil (spontaneous deamination). This can lead to a point mutation if not repaired by the DNA repair enzymes such as uracil glycosylase, which cleaves a uracil in DNA.

When found third in a codon of RNA, cytosine is synonymous with uracil, as they are interchangeable as the third base. When found as the second base in a codon, the third is always interchangeable. For example, UCU, UCC, UCA and UCG are all serine, regardless of the third base.

Cytosine can also be

• EINECS number 200-749-5

• Cytosine MS Spectrum

External links and Citations

References

The implications of deamination on 5-hydroxymethylcytosine, on the other hand, remains less understood. [6]