Radioactive labeling technique

Some further details are the following. Film nonideality may be allowed for [192]. There may be a chemical activation barrier to the transfer step from monolayer to subsurface solution and hence also for monolayer formation by adsorption from solution [294-296]. Dissolving rates may be determined with the use of the radioactive labeling technique of Section III-6A, although precautions are necessary [297]. 

Electron transfer from the amine to flavin would result in the aminium radical which is expected to rearrange rapidly to radical 61. Inactivation of the enzyme would then occur via coupling of the radical with the flavin radical anion resulting in the formation of 66. Coupling of the aminium radical with an amino acid radical would result in the formation of 65. By use of radioactive labeling techniques Silverman et al. have confirmed the formation of 65 and 66 this confirms the role of electron transfer in the oxidation process. Similar studies have been performed using 1-phenylcyclobutylamine (Scheme 18) [198]. 

Furthermore, traditional analytical techniques like gas-liquid chromatography (GLC), GLC/mass spectrometry, high-performance liquid chromatography (HPLC) and HPLC/mass spectrometry can only be used on compounds extracted from biological materials after their administration to animals or humans. The use of radioactive labelled techniques, on the other hand, permits the quantification of both extractable and bound compounds. Nevertheless, in order to do this, it is necessary to make additional separations so that the radioactivity can be attributed to a specific compoimd. 

Following IV vinblastine dosing depending upon the radioactive label technique used only 13.6 to 23% of the total dose was excreted in the urine and that excreted in the feces ranged from 9.9 to 41% with 72 hours (101). 

Electrochemical techniques have been used in analytical chemistry for more than 50 yr, but there was little interest in or understanding of them by biologists until the 1970s. A breakthrough occurred in 1973 when Ralph Adams and his colleagues (1) showed that it was possible to implant a working electrode in a rat brain and detect electroactive materials in vivo. This heralded a new chapter in electrochemistry because it now appeared to be possible to study the release of neurotransmitters in intact animals without the use of complicated radioactive labeling techniques. 

At the same time that individual plants may be studied, various plant organs and tissues can be examined. Immunological methods and radioactive labeling techniques can be used to detect compounds at the cellular level. ELISA (enzyme-linked immunosorbent assay) serves to localize the site of accumulation of secondary metabolites by binding specific antibodies to a solid surface (Wilkinson et al., 1992). 

A difficulty in the physicochemical study of penetration is that the amount of soluble component present in the monolayer is not an easily accessible quantity. It may be measured directly, through the use of radioactive labeling (Section III-6) [263, 266], but the technique has so far been used only to a limited extent. 

Physical methods Physical methods include photometric absorption and fluorescence and phosphorescence inhibition, which is wrongly referred to as fluorescence quenching [1], and the detection of radioactively labelled substances by means of autoradiographic techniques, scintillation procedures or other radiometric methods. These methods are nondestructive (Chapt. 2). 

Isotopic tracers are not exclusively radioactive. For instance, is a nonradioactive element that is suitable for a nonradioactive labeling technique. 

In this study, adsorption of acetic acid under voltammetric conditions was observed by a vibrational technique for the first time. The first work in the field was carried out using FTIR (potential difference infrared spectroscopy, PDIRS) and by radioactive labeling [Corrigan et al., 1988]. Both techniques... 

Radioactive tracer techniques. In electrochemistry, the procedure is essentially the same as in studies of chemical reactions the electroactive substance or medium (solvent, electrolyte) is labelled, the product of the electrode reaction is isolated and its activity is determined, indicating which part of the electroactive substance was incorporated into a given product or which other component of the electrolysed system participated in product formation. Measurement of the exchange current at an amalgam electrode by means of a labelled metal in the amalgam (see page 262) is based on a similar principle. 

A related approach is realized in filter binding assays. Here the reaction solution is filtered, e.g., through nitrocellulose where proteins are absorbed, while small molecules can pass. One example of this technique is the quantification of protein bound and free nucleotides (with radioactive labeled ligands). 

Recently, radioassay methods have been refined to measure folates in biological samples. These techniques use radioactively labeled folates and competitive protein binding.80 Johnson et al.81 compare this method with traditional microbiological assay with L. casei. 

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