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Carbon-14, C-14, 14 C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples.
The equation for the radioactive decay of 14 C is: [17] 14 6 C → 14 7 N + e − + ν e. By emitting a beta particle (an electron, e −) and an electron antineutrino (ν e), one of the neutrons in the 14 C nucleus changes to a proton and the 14 C nucleus reverts to the stable (non-radioactive) isotope 14 N. [18]
Carbon-14 labeling is common in drug development to do ADME (absorption, distribution, metabolism and excretion) studies in animal models and in human toxicology and clinical trials. Since tritium exchange may occur in some radiolabeled compounds, this does not happen with carbon-14 and may thus be preferred.
All living cells contain both DNA and RNA (except some cells such as mature red blood cells), while viruses contain either DNA or RNA, but usually not both. [15] The basic component of biological nucleic acids is the nucleotide , each of which contains a pentose sugar ( ribose or deoxyribose ), a phosphate group, and a nucleobase . [ 16 ]
Radioactive nonprimordial, but naturally occurring on Earth. 61 347 Carbon-14 (and other isotopes generated by cosmic rays) and daughters of radioactive primordial elements, such as radium, polonium, etc. 41 of these have a half life of greater than one hour. Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful radiotracers. 662 989
DNA uses the deoxynucleotides C, G, A, and T, while RNA uses the ribonucleotides (which have an extra hydroxyl(OH) group on the pentose ring) C, G, A, and U. Modified bases are fairly common (such as with methyl groups on the base ring), as found in ribosomal RNA or transfer RNAs or for discriminating the new from old strands of DNA after ...
[citation needed] Silicon biochemistry (Organosilicon) Alternative biochemistry Silicon-based life Like carbon, silicon can create molecules that are sufficiently large to carry biological information; however, the scope of possible silicon chemistry is far more limited than that of carbon. [citation needed] Silicon dioxide biochemistry
Has no known biological role; as it is radioactive with a short half-life, it is very rare and is seldom present for long. [11] Radioactive. [11] protactinium: 91: 1b: Has no known biological role; as it is radioactive with a short half-life, it is very rare and is seldom present for long. [11] Both toxic and highly radioactive. radium: 88: 1bc