Carbon-14 Carbon-14 Carbon-14, (C), or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934. There are three naturally occurring isotopes of carbon on Earth: carbon-12, which makes up 99% of all carbon on
Stable-isotope probing Stable-isotope probing Stable-isotope probing (SIP) is a technique in microbial ecology for tracing fluxes of nutrients in biogeochemical cycling by microorganisms. A substrate is enriched with a heavier stable isotope that is consumed by the organisms to be studied. Biomarkers with the heavier isotope incorporated into them can be separated from biomarkers containing the more naturally abundant lighter isotope by isopycnic centrifugation. For example, CO can be used to find out which organisms are actively photosynthesizing or consuming new photosynthate. As the biomarker, DNA with C is then separated from DNA with C by centrifugation. Sequencing the DNA identifies which