Cytosine Deoxyribonucleic acid

Chemotherapeutic agents are grouped by cytotoxic mechanism. The alkylating agents, such as cyclophosphamide [50-18-0] and melphalan [148-82-3] interfere with normal cellular activity by alkylation deoxyribonucleic acid (DNA). Antimetabohtes, interfering with complex metaboHc pathways in the cell, include methotrexate [59-05-2] 5-fluorouracil [51-21-8] and cytosine arabinoside hydrochloride [69-74-9]. Antibiotics such as bleomycin [11056-06-7] and doxombicin [23214-92-8] h.a.ve been used, as have the plant alkaloids vincristine [57-22-7] and vinblastine [865-21-4]. 

The sugars are typically ribose (ribonucleic acids, RNA), or 2-deoxyribose (deoxyribonucleic acids, DNA). There are five common bases in nucleic acids adenine (A) thymine (T) uracil (U) cytosine (C) and guanine (G). DNA polymers incorporate the four bases. A, T, C, and G, and RNA, the set A, U, C, and G. 

Cytosine was isolated from hydrolysis of calf thymus in 1894 and by 1903 its structure was known and it had been synthesized from 2-ethylthiopyrimidin-4(3H)-one. The acid hydrolysis of ribonucleic acid gives nucleotides, among which are two cytidylic acids, 2 -and 3 -phosphates of cytidine further hydrolysis gives cytidine itself, i.e. the 1-/3-D-ribofuranoside of cytosine, and thence cytosine. The deoxyribonucleic acids likewise yield deoxyribonucleotides, including cytosine deoxyribose-5 -phosphate, from which the phosphate may be removed to give cytosine deoxyriboside and thence cytosine. 

Hydroxymethylcytosine (967) was isolated only in 1952 from the T-even bacteriophages of Escherichia coli, in which it occurs instead of cytosine in the 2-deoxyribonucleic acid (65MI21304). Of several syntheses described, the most convenient is probably that beginning with ethyl 4-amino-2-methylthiopyrimidine-5-carboxylate which is reduced by LAH to 4-amino-2-methylthiopyrimidin-5-ylmethanol followed by hydrolysis to 5-hydroxymethyl-cytosine (967) (B-68MI21302, B-68MI21306). 

As is well-known, nucleic acids consist of a polymeric chain of monotonously reiterating molecules of phosphoric acid and a sugar. In ribonucleic acid, the sugar component is represented by n-ribose, in deoxyribonucleic acid by D-2-deoxyribose. To this chain pyrimidine and purine derivatives are bound at the sugar moieties, these derivatives being conventionally, even if inaccurately, termed as pyrimidine and purine bases. The bases in question are uracil (in ribonucleic acids) or thymine (in deoxyribonucleic acids), cytosine, adenine, guanine, in some cases 5-methylcytosine and 5-hydroxymethylcyto-sine. In addition to these, a number of the so-called odd bases occurring in small amounts in some ribonucleic acid fractions have been isolated. 

For various reasons, the generalizations mentioned above must be regarded as strictly provisional. Analyses utilizing formic acid indicate the presence of more than one phosphorus atom per purine or pyrimidine residue. This discrepancy, it is pointed out, could equally well result from an apparent deficiency of bases, due to error in the analytical technique.160 It is also necessary to consider that some nucleic acids are now known to contain more bases than was previously realized. Thus, 5-(hydroxymethyl)-cytosine is present in various viruses,181-182 and 5-methylcytosine occurs in various animal and plant deoxyribonucleic acids but is absent from those of microbial origin.17-160-1M- 184- 186 Certain microbial deoxyribonucleic acids also contain 6-methylaminopurine.186a Various bacteriophage deoxyribonucleic acids have been found to contain a component which is believed to consist of a D-glucoside186b of 5 -(hydroxymethyl)cytidylic acid. 

DNA, short for deoxyribonucleic acid, is the coding machinery of life. The beauty of DNA is in its simplicity that results in the complexity of life. The double helix of DNA is made of the chemicals adenine (A), guanine (G), thymine (T), and cytosine (C). These chemical are bound in long stretches as AT and CG pairs,... 

DNA (deoxyribonucleic acid)—Carrier of genetic material that determines inheritance of traits. DNA is in chromosomes in every cell of the body except red blood cells and is copied when cells divide. DNA molecules are shaped like a double helix, and are composed of sequences of four bases adenosine (A), cytosine (C), guanine (G), and thymine (T). The sequence of the bases directs production of particular proteins by determining the sequence of amino acids in proteins. The double-helk structure of DNA helps it transmit genetic information. 

The most important pyrimidine derivatives are those upon which biological organisms depend. Cytosine 1018 and uracil 1019 are found in ribonucleic acid (RNA) in the form of their ribonucleotides, cytidine 1020 and uridine 1021, while in deoxyribonucleic acid (DNA), cytosine and thymine 1022 are found in the form of their 2 -deoxyribonucleotides, 2 -deoxycytidine 1023 and thymidine 1024. 5-Methylcytosine 1025 is also found to a small extent (c. 5%) in human DNA in the form of its 2 -deoxyriboside 1026, and 5-(hydroxymethyl)cytosine-2 -deoxyriboside 1027 has also been detected in smaller amounts <2005CBI1>. Many variants of cytosine and uracil can be found in RNA including orotic acid 1028 in the form of its ribonucleotide orotidine 1029. Other pyrimidine derivatives to have been isolated from various biological sources include 2 -deoxyuridine 1030, alloxan 1031, and toxopyrimidine (pyramine) 1032 (Figure 2). 

Nucleic Acid. A nucleic acid is a natural polynucleotide. It is a sugar-phosphate chain with purine and pyrimidine bases attached to it, as shown in Chart 10. If the sugar is deoxyribose and the pyrimidine bases are cytosine and thymine, the nucleic acid is deoxyribonucleic acid, DNA if the sugar is ribose, and the pyrimidine bases are (mostly) cytosine and uracil, the nucleic acid is ribonucleic acid, RNA. The sequence of bases may appear arbitrary and random, but it constitutes a meaningful code (see Code Word). In double-stranded nucleic acids,... 

Density of states weighted Franck-Condon factor Deoxyribonucleic acid Barrier height for the adiabatic hole motion Difference in ionization potentials of adenine-thymine and guanine-cytosine base pairs... 

If the terminal pyrophosphate is removed from a molecule of ATP, the remainder is AMP, adenosine monophosphate, one of the four building blocks of the important biological macromolecules, the nucleic acids. There are two types of nucleic acids (26) ribonucleic acid (RNA), and deoxyribonucleic acid (DNA). RNA is a polymer of four different nucleotides, one of which is AMP, the ribose phosphate of adenine. The other three nucleotides are also ribose phosphates of heterocyclic bases, guanine, cytosine, and uracil. The structure of the four bases is shown in Figure 6. 

The pyrimidines found in the deoxyribonucleic acids are thymine and cytosine, and the purines are adenine and guanine. Their structures have been discussed in Section 8-8. 

The basic monomers of nucleic acids are nucleotides which are made up of heterocyclic nitrogen-containing compounds, purines and pyrimidines, linked to pentose sugars. There are two types of nucleic acids and these can be distinguished on the basis of the sugar moiety of the molecule, Ribonucleic acids (RNA) contain ribose, while deoxyribonucleic acid (DNA) contains deoxyribose. The bases cytosine (C) adenine (A) and guanine (G) are common in both RNA and DNA. However, RNA molecules contain a unique base, uracil (U), while the unique DNA base is thymidine (T). These differences in the base structure markedly affect the secondary structures of these polymers. The structures of DNA and RNA are outlined in Appendix 5.2. 

Cytosine, a constituent of deoxyribonucleic acid (DNA) can be represented by the molecular model at the top of the next column. If 0.001 mol of cytosine is submitted to combustion analysis, how many moles of CO2 and how many moles of H2O would be formed ... 

Cullis PM, McClymont JD, Malone ME, Mather AN, Podmore ID, Sweeney MC, Symons MCR (1992) Effects of ionizing radiation on deoxyribonucleic acid. Part 7. Electron capture at cytosine and thymine. J Chem Soc Perkin Trans 2 1695-1702... 

Dizdaroglu M, Holwitt E, Hagan MP, Blakely WF (1986) Formation of cytosine glycol and 5,6-di-hydroxycytosine in deoxyribonucleic acid on treatment with osmium tetroxide. Biochem J 235 531-536... 

Of these pyrimidines, uracil and cytosine are constituents of ribonucleic acid, whereas thymine and cytosine are components of deoxyribonucleic acid. It was generally accepted that these nitrogenous heterocycles were the only pyrimidine components of the nucleic acids. The possibility that the nucleic acids might contain moieties other than those described had been voiced by Gulland,26 Chargaff and Vischer,27 and Davidson.28 The... 

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