Цитозин

Описание

Cytosine is pyrimidine; along with adenine and guanine they account for the fi ve nucleic acid bases. Pyrimidines are heterocyclic single-ringed compounds based on the structure of pyrimidine. Cytosinelike adenine and guanine, form nucleosides and nucleotides in RNA and DNA. When the bases combine with ribose, a ribonucleoside forms; and when it attaches to deoxyribose, a deoxyribosenucleoside is formed. Names of the nucleoside are summarized in Table 29.1.these in turn combine with phosphoryl groups, in a process called phosphorylation, to form their respective nucleotides that form nucleic acids.the nucleotides can be tri, di, and mono phosphate nucleotides similar to the way in which adenine forms ATP, ADP, and AMP.

Химические свойства

White Solid

История

Cytosine is first isolated by hydrolysis of calf thymus tissue by Albrecht Kossel (1853–1927) and A. Neumann during 1893–1894. Thymine’s structure was published in 1900 and confi rmed over the next several years when it was synthesized by several investigators. In 1903, cytosine was synthesized by Henry Lord Wheeler (1867–1914) and Treat B. Johnson, confirming its structure. Uracil was first isolated in 1900 from yeast nucleic acid found in bovine thymus and herring sperm.the methylation of uracil produces thymine; thymine is also called 5-methyluracil because methylation takes place at the fi fth carbon in uracil to produce thymine.

Использование

Cytosine is a nucleoside used for proteomics research. It is also used as an enzyme substrate or precursor of effector molecules such as cytosine sugars.

Определение

A nitrogenous base found in DNA and RNA. Cytosine has the pyrimidine ring structure.

Общее описание

Pharmaceutical secondary standards for application in quality control, provide pharma laboratories and manufacturers with a convenient and cost-effective alternative to the preparation of in-house working standards.

Методы очистки

Cytosine crystallises from H2O as the monohydrate which loses water on heating above 100o. Its solubility in H2O is 0.77%. UV: max 267nm ( 6,100) in H2O pH 8.8 and 275nm ( 10,400) in 0.1N HCl. [Hilbert & Johnson J Am Chem Soc 52 1152 1930, Hilbert et al. J Am Chem Soc 57 552 1935, Beistein 25 III/IV 3654.]

Структура и конформация

Cytosine is a pyrimidine containing a single heterocyclic aromatic ring, a keto group at C2, and an amine group at C4. The molecule is planar in shape. Cytosine can form three hydrogen bonds with guanine. Due to these three hydrogen bonds, the cytosine-guanine base pair has an overall higher boiling point and greater bond strength than the adenine-thymine base pair. The high melting point makes the cytosine-guanine base-pair much more resistant to denaturation. The double strand of DNA breaks down into its single constituent strands due to high temperatures.