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Pyrimidine (C 4 H 4 N 2; / p ɪ ˈ r ɪ. m ɪ ˌ d iː n, p aɪ ˈ r ɪ. m ɪ ˌ d iː n /) is an aromatic, heterocyclic, organic compound similar to pyridine (C 5 H 5 N). [3] One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring.
RNA is composed of pyrimidine and purine nucleotides, both of which are necessary for reliable information transfer, and thus natural selection and Darwinian evolution. Becker et al. showed how pyrimidine nucleosides can be synthesized from small molecules and ribose , driven solely by wet-dry cycles.
Pyrimidine degradation ultimately ends in the formation of ammonium, water, and carbon dioxide. The ammonium can then enter the urea cycle which occurs in the cytosol and the mitochondria of cells. [5] Pyrimidine bases can also be salvaged. For example, the uracil base can be combined with ribose-1-phosphate to create uridine monophosphate or UMP.
Left: The structure of pyrimidine with the locants for ring atoms marked. Right : 5-Fluorouracil , a fluoropyrimidine formally named as 5-fluoro-1 H ,3 H -pyrimidine-2,4-dione Fluoropyrimidines are a general class organic compounds in which the substituent (s) around a pyrimidine ring include at least one fluorine atom.
Pyrimidine dimers encompass several types, each with distinct structures and implications for DNA integrity. [ citation needed ] Cyclobutane pyrimidine dimer (CPD) is a dimer which features a four-membered ring formed by the fusion of two double-bonded carbons from adjacent pyrimidines.
The nucleobases are classified into two types: the purines, A and G, which are fused five- and six-membered heterocyclic compounds, and the pyrimidines, the six-membered rings C and T. [12] A fifth pyrimidine nucleobase, uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring.
It is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, as well as in pyrimidine nucleotide formation. Hence it is a building block for DNA and RNA. [1] [2] [3] The vitamins thiamine [4] and cobalamin, [5] and the amino acid tryptophan also contain fragments derived from PRPP. [6]
Thymidine (symbol dT or dThd), also known as deoxythymidine, deoxyribosylthymine, or thymine deoxyriboside, is a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine (A) in double-stranded DNA. In cell biology it is used to synchronize the cells in G1/early S phase.