Radioactive compounds, commercially

Most of the indexed information originates in advertisements to hire chemists or to sell goods or services. The latter ads make it clear that their sponsors employ organic chemists as discovery or development researchers. For example, a commercial offer to make C-labeled drugs for metabolism studies requires synthetic chemists trained in handling radioactive compounds. 

Autoradiography is a technique for locating radioactive compounds within cells it can be conducted with light or electron microscopy. Living cells are first exposed to a radioactive precursor of some intracellular component. The labeled precursor is a compound with one or more hydrogen ( H) atoms replaced by the radioisotope tritium ( H) e.g., [ H] thymidine is a precursor of DNA, and [ H] uridine is a precursor of RNA (Chap. 3). Various tritiated amino acids are also commercially available. The precursors enter the cells and are incorporated into the appropriate macromolecules. The cells are then fixed and the samples embedded in a resin or wax and then sectioned into thin slices. 

It was concluded that the SMM-modifled membranes could be used effectively for rejecting the radioactive compounds in water solutions. Moreover, the radioactivity of the SMMs membranes after 4 h DCMD experiments was substantially lower than that of the commercial membrane TF200 (Table 1.4), suggesting a smaller adsorption of the radionuclides on the SMM-modifled membrane, which can be regarded as an advantageous property and important for further application in nuclear technologies. 

A brochure published by the International Atomic Energy Agency lists the commercially available preparations, their specific activities and the manufacturers addresses [312]. The commercially available preparations are often very impure and can be used for chemical and biochemical studies only after careful purification. The classical methods for processing crude synthetic products are generally imsatisfactory when applied to small amounts of radioactive compounds. TLC is particularly convenient for purifying radioactive compounds. A detailed account of such preparative applications of the method is given in a special section of this chapter. 

In 1961/62, the considerable impurity of many of the radioactively labelled compounds commercially available at that time, was demonstrated with the help of TLC [424,... 

A modem variant is to count the number of atoms directly in a mass spectrometer.) The practical limit is about 50000 y since by this time the activity has fallen to about 0.2% of its original valuable and becomes submerged in the background counts. is also extremely valuable as a radioactive tracer for mechanistic studies using labelled compounds, and many such compounds, particularly organic ones, are commercially available (p. 310). 

Of more chemical interest is the synthesis of radioactive " C compounds from " C02 which is conveniently stored as a carbonate. " C is generated by an (n,p) reaction on a nitride or nitrate in a nuclear reactor (see p. 1256). More than 500 compounds specifically labelled with " C are now available commercially, the starting point of many of the syntheses being one of the following reactions ... 

In addition to the 4 stable isotopes sulfur has at least 9 radioactive isotopes, the one with the longest half-life being which decays by activity (Kmax 0.167 MeV, 87.5 d). can be prepared by Cl(n,p), S(n,> ) or S(d,p) and is commercially available as SeicmcQt H2S, SOCb and KSCN. The radiation has a similar energy to that of C ( mav 0.155 MeV) and similar counting techniques can be used (p. 276). The maximum range is 300 min in air and 0.28 mm in water, and effective shielding is provided by a perspex screen 3-10 mm thick. The preparation of many - S-containii compounds has been... 

The only respect in which the hot atom chemistry of organometallic compounds has so far been applied to other fields of study is in the area of isotope enrichment. Much of this has been done for isolation of radioactive nuclides from other radioactive species for the purpose of nuclear chemical study, or for the preparation of high specific activity radioactive tracers. Some examples of these applications have been given in Table II. The most serious difficulty with preparation of carrier-free tracers by this method is that of radiolysis of the target compound, which can be severe under conditions suited to commercial isotope production, so that the radiolysis products dilute the enriched isotopes. A balance can be struck in some cases, however, between high yield and high specific activity (19, 7J),... 

Another application for adsorption of metal impurities is in the nuclear power industry. Radioactive cesium is one of the compounds that is difficult to remove from radioactive waste. This is because ordinary resins and zeolites do not effectively adsorb radioactive cesium. In 1997, lONSlV lE-911 crystalline silicotitan-ate (CST) ion exchangers were developed and effectively used to clean up radioactive wastes in the Melton Valley tanks at Oak Ridge [268, 269], CST was discovered [270] by researchers at Sandia National Laboratories and Texas A M University, with commercial manufacture carried out by UOP. 

Astatine does not have stable or useful compounds. Like a halogen, it will form halogen salts with a few other elements. No significant astatine commercial compounds have been produced with the exception of astatine-211, which has a half-life of just over seven hours and is used as a radioactive tracer for thyroid diseases. 

The metal has very little commercial use. In elemental form it is a laser source, a portable x-ray source, and as a dopant in garnets. When added to stainless steel, it improves grain refinement, strength, and other properties. Some other applications, particularly in oxides mixed with other rare earths, are as carbon rods for industrial hghting, in titanate insulated capacitors, and as additives to glass. The radioactive isotope ytterbium-169 is used in portable devices to examine defects in thin steel and aluminum. The metal and its compounds are used in fundamental research. 

PEAT, Inc., has developed the thermal destruction and recovery (TDR) system for the treatment of medical, hazardous, and radioactive wastes. An electronic plasma heating system is used to break down wastes into three phases. The ceramic, metal, and off-gas phases can aU be used as commercial products. The technology has been evaluated in treatability studies on infectious medical waste. Department of Defense (DOD) ammunition and energetic materials, U.S. Department of Energy (DOE) weapon components, ash, electronic scrap, batteries, asbestos, and organic compounds. 

Soil flushing is a commercially available, in situ technology for the treatment of soils contaminated with inorganic compounds including radioactive contaminants. The technology can also be used to treat volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs),... 

The use of radiolabeled nucleosides as markers for anticancer activity has become a popular method due to the commercial availability of such compounds. The technique is based upon the knowledge that cells rendered unable to replicate or killed by the anticancer agent are unable to effectively incorporate nucleic acid precursors into their DNA or RNA structure. Therefore, a decrease in cell viability correlates with a decrease in radioactivity relative to a control cell population. Although specific procedures differ, the basic technique involves the incubation of tumor cells in the presence of the radiolabeled compound with or without anticancer agent followed by scintillation counting to determine the radioacti vity of the samples. 

Chemical synthesis of labeled compounds suffers from some limitations and problems, though. One limitation concerns the amount and cost of the radioactive starting material. This factor necessitates devising synthetic routes to the desired compounds in which the radiolabel can be introduced near the end of the sequence of reactions, so as to secure as high an overall yield of labeled material as possible. At present, numerous labeled compounds are available commercially as starting materials for syntheses. Still, in planning a new synthetic route, it is necessary to consider its compatibility with the specific stalling material available. 

Thus, there were serotonin 1 receptors, and then there were 1 and 2 receptors, and then la and lb and 2a and 2b receptors, and on and on. These are called 5-HT receptors, since the chemical name for serotonin is 5-hy-droxytryptamine, and the scientist would never want to let the layman know just what he is talking about. DOI has been synthesized with a variety of radioactive iodine isotopes in it, and these tools have been of considerable value in mapping out its brain distribution. And by extrapolation, the possible localization of other psychedelic compounds that cannot be so easily labelled. A small neurochemical research company on the East Coast picked up on these properties of DOI, and offered it as a commercial item for research experiments. But I doubt that they are completely innocent of the fact that DOI is an extremely potent psychedelic and that it is still unrecognized by the Federal drug laws since, in their most recent catalog, the price had almost doubled and a note had been added to the effect that telephone orders cannot be accepted for this compound. 

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