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
Tritium section for thermal neutrons is about 0.52 millibarns, whereas that of oxygen-16 () is about 0.19 millibarns and that of oxygen-17 () is about 240 millibarns. Tritium is an uncommon product of the nuclear fission of uranium-235, plutonium-239, and uranium-233, with a production of about one atom per each 10,000 fissions. The release or recovery of tritium needs to be considered in the operation of nuclear reactors, especially in the reprocessing of nuclear fuels and in the storage of spent nuclear fuel. The production of tritium is not a goal, but rather a side-effect. It is discharged to the atmosphere