Product Code Database
Uracil () (symbol U or Ura) is one of the four in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two . In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine.
Uracil is a common and naturally occurring pyrimidine derivative. The name "uracil" was coined in 1885 by the German chemist Robert Behrend, who was attempting to synthesize derivatives of uric acid. Originally discovered in 1900 by Alberto Ascoli, it was isolated by hydrolysis of yeast nuclein; it was also found in bovine thymus and spleen, herring sperm, and wheat Cereal germ. It is a planar, unsaturated compound that has the ability to absorb light.
Uracil that was formed extraterrestrially has been detected in the Murchison meteorite, in near-Earth asteroid Ryugu, and possibly on the surface of the moon Titan. It has been synthesized under cold laboratory conditions similar to outer space, from pyrimidine embedded in water ice and exposed to ultraviolet light.
Uracil undergoes amide-imidic acid tautomeric shifts because any nuclear instability the molecule may have from the lack of formal aromaticity is compensated by the cyclic-amidic stability. The amide tautomer is referred to as the lactam structure, while the imidic acid tautomer is referred to as the lactim structure. These tautomeric forms are predominant at pH 7. The lactam structure is the most common form of uracil.
Uracil also recycles itself to form nucleotides by undergoing a series of phosphoribosyltransferase reactions. Degradation of uracil produces the substrates β-alanine, carbon dioxide, and ammonia.
Oxidative degradation of uracil produces urea and maleic acid in the presence of H2O2 and Iron2+ or in the presence of diatomic oxygen and Fe2+.
Uracil is a weak acid. The first site of ionization of uracil is not known. (1973). 9780471984184, Wiley-Interscience. ISBN 9780471984184 The negative charge is placed on the oxygen anion and produces a p Ka of less than or equal to 12. The basic p Ka = −3.4, while the acidic p Ka = 9.389. In the gas phase, uracil has four sites that are more acidic than water.
This problem is believed to have been solved in terms of evolution, that is by "tagging" (methylating) uracil. Methylated uracil is identical to thymine. Hence the hypothesis that, over time, thymine became standard in DNA instead of uracil. So cells continue to use uracil in RNA, and not in DNA, because RNA is shorter-lived than DNA, and any potential uracil-related errors do not lead to lasting damage. Apparently, either there was no evolutionary pressure to replace uracil in RNA with the more complex thymine, or uracil has some chemical property that is useful in RNA, which thymine lacks. Uracil-containing DNA still exists, for example in:
The most common way to synthesize uracil is by the condensation of malic acid with urea in fuming sulfuric acid:
Uracil can also be synthesized by a double decomposition of thiouracil in aqueous chloroacetic acid.
Photodehydrogenation of 5,6-diuracil, which is synthesized by beta-alanine reacting with urea, produces uracil.
Based on 12C/13C of organic compounds found in the Murchison meteorite, it is believed that uracil, xanthine, and related molecules can also be formed extraterrestrially. Data from the Cassini mission, orbiting in the Saturn system, suggests that uracil is present on the surface of the moon Titan. In 2023, uracil was observed in a sample from 162173 Ryugu, a near-Earth asteroid, with no exposure to Earth's biosphere, giving further evidence for synthesis in space.
Uracil readily undergoes addition to ribose and to partake in synthesis and further reactions in the body. Uracil becomes uridine, uridine monophosphate (UMP), uridine diphosphate (UDP), uridine triphosphate (UTP), and uridine diphosphate glucose (UDP-glucose). Each one of these molecules is synthesized in the body and has specific functions.
When uracil reacts with anhydrous hydrazine, a first-order kinetic reaction occurs and the uracil ring opens up. If the pH of the reaction increases to > 10.5, the uracil anion forms, making the reaction go much more slowly. The same slowing of the reaction occurs if the pH decreases, because of the protonation of the hydrazine. The reactivity of uracil remains unchanged, even if the temperature changes. (1972). 9781468429756, Plenum Press. ISBN 9781468429756
Uracil can be used for drug delivery and as a pharmaceutical. When elemental fluorine reacts with uracil, they produce 5-fluorouracil. 5-Fluorouracil is an anticancer drug (antimetabolite) used to masquerade as uracil during the nucleic acid replication process. Because 5-fluorouracil is similar in shape to, but does not undergo the same chemistry as, uracil, the drug inhibits RNA transcription enzymes, thereby blocking RNA synthesis and stopping the growth of cancerous cells. Uracil can also be used in the synthesis of caffeine. Uracil has also shown potential as a HIV viral capsid inhibitor. Uracil derivatives have antiviral, anti-tubercular and anti-leishmanial activity.
Uracil can be used to determine microbial contamination of . The presence of uracil indicates lactic acid bacteria contamination of the fruit. Uracil derivatives containing a diazine ring are used in . Uracil derivatives are more often used as antiphotosynthetic , destroying weeds in cotton, sugar beet, , soybean, , sunflower crops, , berry plantations, and . (1997). 9780471960348, John Wiley and Sons. ISBN 9780471960348 Uracil derivatives can enhance the activity of antimicrobial Polysaccharide such as chitosan.
In yeast, uracil concentrations are inversely proportional to uracil permease.
Mixtures containing uracil are also commonly used to test reversed-phase HPLC columns. As uracil is essentially unretained by the non-polar stationary phase, this can be used to determine the dwell time (and subsequently dwell volume, given a known flow rate) of the system.
|
|
