Radioisotope tagging

However, affinity, photochemical, or radioisotope tags can also be used. After removal of unbound molecules in solution, the microarrays are subject to detection to determine the binding of target molecules, or the target molecule-induced alteration of live cells in the microarrays. These interactions are usually detected and quantified by the fluorescence of fiuorophore-labeled target molecules. Fluorescent detection is sensitive, can have high resolution, and is compatible with many fluorescence-based microarray scanners. 

Monk, C. D. 1967. Radioisotope tagging through seed soaking. Bull. Ga. Acad. Sci. 25(1) 13-17. 

Sonenshine, D. E. 1971. Mass rearing of radioisotope-tagged larval ticks for ecological investigations. J. Econ. Entomol. 64(6) 1423-1429. 

Positron emission tomography (PET) is an imaging technique that relies on the emission of positrons from radionucleotides tagged to an injectable compound of interest. Each positron emitted by the radioisotope collides with an electron to emit two photons at 180° from each other. The photons are detected and the data processed so that the source of the photons can be identified and an image generated showing the anatomical localization of the compound of interest. 

The radioisotope Cr was used to tag the species and the separation of Cr from CrX " was achieved using an ion-exchange method, after oxidation of the Cr to Cr with Fe(III) or oxygen. The reactions were carried out in the absence of oxygen in perchlorate media. For the systems involving chloride, fluoride, and azide . King et al. have found a rate law... 

Phosphorus-32, the most important radioisotope of phosphorus, has a half-life of 14 days. It provides beta radiation (high-speed electrons) and is made by inserting phosphorus into nuclear reactor piles. P-32 is used as a tag to trace biochemical reactions in patients. It is also used to treat leukemia and skin and thyroid diseases. 

Several clinical trials have evaluated (or continue to evaluate) monoclonal antibodies to which a radioactive tag has been conjugated. These are usually employed as potential anti-cancer agents. The rationale is selective delivery of the radioactivity directly to the tumour site. Most of the radioisotopes being evaluated are /i-emitters these include I and I (iodine), Re and Re (rhenium) and (yttrium). The medium-energy radioactivity these emit is capable of penetrating... 

The probe species is often radioactively labeled, or it may carry a fluorescent tag, or some other chemical or enzymatic moiety to generate a positional signal. For radioactive labeling, a common choice of radioisotope is phosphorus-32 (or 32P), because it can be incorporated as phosphate into DNA or RNA relatively easily, and it emits energetic beta particles that are easy to detect. The radioactivity on the membrane can be used to expose an adjacent x-ray film in a pattern corresponding to the radioactive spots on the membrane. After a suitable exposure time, one develops the film and studies the location and intensity of the images of the radioactive spots to deduce the position and degree of probe hybridization on the membrane. 

Here, the antibody-antigen reactions are observed indirectly by use of labels which are attached to either the antibody or antigen. The labels can be conjugated covalently and include radioisotopes, enzymes, labeled second antibodies, fluorescent tags, luminescent molecules and phages (12, 41, 45, 48). The use of labels helps in increasing the sensitivity of the assays considerably compared to the precipitation or agglutination assays. 

The sensitivities of the label-based approach depend mainly on the specific activity of the labels linked to the oligonucleotide probe. Radioisotopic [48], fluorescent [50] and enzymatic [38,40,47] labels have been commonly used. Besides the above labels, NPs have attractive properties to act as DNA tags [18,51]. The fact that NPs present an excellent biocompatibility with biomolecules and display unique structural, electronic, magnetic, optical and catalytic properties have made them a very attractive material to be used as label [52,53]. 

The radiation emitted from decay of single atoms can be easily measured. Thus, small amounts of radioisotopes can be incorporated into systems to study, for example, chemical reactions and the flow of fluids through complex systems such as organs of the human body. They also can be used in more mundane applications such as locating leaks in buried piping. Many organic compounds tagged with... 

Laurence s cyclotron had manufactured many other radioisotopes, but this factory was a very slow and inefficient one compared with a nuclear furnace. With the invention of the nuclear reactor several hundreds of brand new atomic species or isotopes were created for the first time and made available to scores of research centers. The radioactive isotope turned out to be a new, revolutionary, and extremely delicate tool in scientific research. It is used in the so-called tracer or tagged-atom technique. For example, radioactive sodium-24 is substituted for the normal sodium-23 atoms in a bit of... 

Numerous trace elements are known to be nutritionally essential in man In order to assess the essentiality, dietary availability, and metabolic fate of these, means of labeling for subsequent identification are needed In animal studies, radioisotopes are often used for this purpose, but their use in human studies is generally contraindicated due to the radiation hazards An alternate method is to use stable isotopes of the elements, which overcomes this limitation A method will be described for conveniently measuring the stable isotopes of selenium, permitting their use as metabolic tags in tracer studies Using one stable isotope as the tracer and another as internal standard, one can quantitatively identify in a sample the tracer, natural (unenriched) selenium present with it, and total selenium Some of the kinds of information obtainable from metabolic tracer studies will be discussed ... 

GPC (TAG) increased the amount of radioisotopically labeled macromolecules that was released from the cells from 30-32% up to 55%, and increased the release of labeled lipids from 9-12% up to 19% (Table VA). The indentity of the I-labeled lipid molecules released from the cells after antibody-GPC treatment is shown in Table VB TAG released a significantly higher proportion of sphingomyelin, phosphatidylserine, and... 

Q.3.5 The PET (positron emission tomography) scanner uses a tagged radioisotope to measure glucose delivery to similar regions of the brain during brain tasks . Is this a better system for observing intellectual function than those described in Question 3.4 ... 

Simultaneous detection of different probes is possible with different fluorescent tags, enzymes, radioisotopes or combinations thereof. Double-label ISH with radioisotopes can be achieved by exploiting the difference in energy of the nuclides. For example, a thin layer of clear plastic over the specimen prevents H from penetrating the emulsion while S can be recorded in the second layer. Haase et al. (1985) fine-tuned this technique by color microautoradiography in which grains in the first layer are converted to a magenta color and those in the second layer to a cyan color. 

Radioisotopes used as tracers solve scientific mysteries Radioactive and nonradioactive isotopes of the same element act the same way in a chemical reaction. When scientists want to put tags on a compound, they substitute a radioactive isotope for a nonradioactive one in the compound. Then they can use radiation detectors to track and locate the radioisotope tracer. 

Linked with the previous basic description on antibodies, there is an other form of labelling, which employs an enzyme rather than a radioisotope. In this case the tag (the enzyme) is enormous with respect to the subject molecule. Since the concentrations are very low, recovery is undertaken using an antibody. The best known methodology of this type is the enzyme-linked immunosorbent assay... 

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