Crossover experiment (chemistry) or phosphine. The mechanisms of enzyme-catalyzed reactions can also be studied using crossover experiments. Examples of the application of this technique in biochemistry include the study of reactions catalyzed by nucleoside diphosphohexose-4,6-dehydratases, the aconitase-catalyzed elimination of water from citrate, and various reactions catalyzed by coenzyme B-dependent enzymes, among others. Unlike isotope labeling studies in organic and organometallic chemistry, which typically use deuterium when an isotope of hydrogen is desired, biochemical crossover experiments frequently employ tritium. This is due to the fact that tritium is radioactive and can be tracked using the autoradiographs of gels in gel electrophoresis. Isotope labeling experiments
Beta particle long as the tritium exists (and the phosphors do not themselves chemically change); the amount of light produced will drop to half its original value in 12.32 years, the half-life of tritium. Beta-plus (or positron) decay of a radioactive tracer isotope is the source of the positrons used in positron emission tomography (PET scan). Henri Becquerel, while experimenting with fluorescence, accidentally found out that uranium exposed a photographic plate, wrapped with black paper, with some unknown radiation that could not be turned off like X-rays. Ernest Rutherford continued these experiments and discovered two different kinds of radiation: He published his