Radioactive methods

Tajima and co-workers [108] determined the surface excess of sodium dode-cyl sulfate by means of the radioactivity method, using tritiated surfactant of specific activity 9.16 Ci/mol. The area of solution exposed to the detector was 37.50 cm. In a particular experiment, it was found that with 1.0 x 10" Af surfactant the surface count rate was 17.0 x 10 counts per minute. Separate calibration showed that of this count was 14.5 X 10 came from underlying solution, the rest being surface excess. It was also determined that the counting efficiency for surface material was 1.1%. Calculate F for this solution. 

Radioactivity. Methods based on the measurement of radioactivity belong to the realm of radiochemistry and may involve measurement of the intensity of the radiation from a naturally radioactive material measurement of induced radioactivity arising from exposure of the sample under investigation to a neutron source (activation analysis) or the application of what is known as the isotope dilution technique. 

The radioactive method used in enzymatic studies by Flodgaard and Brodersen (Fll) is based on work of Brodersen (B22) and Brodersen and Jacobsen (B24). Samples of a solution of bilirubin diglucuronoside... 

Otto Hahn, 1879-. President of the Max Planck Society for the Promotion of Science. Discoverer with F. Strassmann, in 1938, of the splitting of uranium and of thorium by neutron irradiation into two elements of medium weight. Discoverer of radioactinium, radiothorium, mesotliorium, uranium Z, and (with Miss Lise Meitner) protactinium. He has devised radioactive methods for determining the geologic and biologic age of materials. In 1945 he received the Nobel Prize for Chemistry for the year 1944. 

Hampton, R.Y. Raetz, C.R.H. Lipid A 4-kinase from Escherichia coli enzyme assay and preparation of 4- 2p-labeled probes of high specific radioactivity. Methods Enzymol., 209, 466-475 (1992)... 

Measurement of Deposit. Common methods used to measure sediments are manual testing, sedimentation balance, radioactive methods, dipping of bodies, and probe tools. 

Herber, R. H., and Hazony, Y., in Physical Methods of Chemistry, Part IIID Optical, Spectroscopic, and Radioactivity Methods (A. Weissberger and B. W. Rossiter, eds.), p. 215. Wiley, New York, 1972. 

The radioactive method may be used when the titration method is not applicable, e.g., when the pH of the reaction is near the pK of pectin (about A.0), or when the reaction rate is low because of limited amount of enzyme or substrate. However, the automatic titration method when applicable, is advantageous because the reaction can be monitored continuously and any deviations from linearity readily recognized. 

Methods for Determining Biomarkers of Exposure and Effect. As discussed above, the presence of radium in biological materials is usually determined by virtue of its radioactivity. Methods available for the determination of radioactivity in biological materials include alpha spectroscopy and gamma spectrometry, which is more convenient, but generally less sensitive, than alpha spectroscopy (Joshi 1987). It would be useful to have additional data on the sensitivity and accuracy of the methods that are currently in use. 

In the chemical method of investigating transfer through boundary layers, the surfaces are coated with slightly volatile substances such as napthalene, bromobenzene or camphor. The rate of evaporation is measured, and related to the driving force xo Xu where xo is the concentration corresponding to the vapour pressure of the substance at the surface temperature and Xi is the (often negligible) concentration in the free air. In the radioactive method, the adsorbed phase is often less than a monolayer, and the vapour pressure exerted by the deposited vapour is negligible. If, however, the surface is not a perfect sink the resistance Xo IQ is called the surface resistance, denoted rs. 

The lines in Fig. 7.4 are the results of theoretical calculations, using models of the respiratory tract (Yu Diu, 1982). The points are measurements with radioactive aerosols. Numerous other determinations of fractional deposition in the whole tract have been made, using non-radioactive methods to count the number of particles in the inhaled and exhaled air (Heyder et al., 1986 Schiller et al., 1988). Fractional deposition is least for particles of about 0.2 to 0.5 m diameter. Table 7.1 shows that the combined effect of sedimentation and Brownian motion is then at a minimum. 

For the membrane array of cytokine expression, the general procedures (Amersham Pharmacia Biotech R D Systems SuperArray Inc., Bethesda, MD Clontech Laboratories, Inc., Palo Alto, CA) include RNA extraction, reverse transcription into biotin- or radioisotope-labeled cDNA, hybridization with about 20 to several hundred different cDNA prespotted membranes, and signal detection using fluorescence or radioactive methods (L3). As an example, Fig. 4 and Table 4 show different chemokine genes upregulated in allergic asthmatic patients compared with normal controls, based on membrane array technology (SuperArray). 

Muller, N., ibid. In Interferometry, Light Scattering, Microscopy, Microwave and Magnetic Resonance Spectroscopy Optical, Spectroscopic and Radioactivity Methods, Chapter VII. 

Grum, F. in Spectroscopy and Spectrometry in the Infrared, Visible and Ultraviolet Optical, Spectroscopic and Radioactivity Methods, Part mB of Physical Methods of Chemistry, which is Vol. I of Techniques of Chemistry Weissberger, H. Rossiter, B. W. Gen. Eds Wiley-Interscience New York, 1972 715 pp. Chapter III. 

The method is only directly applicable to solids which have an element with a radioactive isotope. Kolthoff and O Brien1 used artificially radioactive bromine for estimating the surface of silver bromide it is necessary, here, to have an adsorbed layer of dyestuff, to restrict exchange with the interior. In the case of lead salts the areas deduced by the radioactive method are of the same order of magnitude as those found by microscopic examination the discrepancies may, however, reach 100 or 200 per cent. 

Quantitative analysis has become possible due to technical advances in synthesis of complex molecules with isotopic labels at any one of many specific position and measurements of KIE determined accurately and precisely by mass-spectrometry and radioactive methods. The most informative method for elucidation of the enzyme reaction limiting step and nature of transition-state is the competitive labeled method (Schramm, 1999). This method is based on the use of two labeled preparations of the same substrate, one with the labeled atom at a site expected to experience bonding changes at the TS and a second preparation with a different labeled atom at a site remote from the bond-breaking site. Many molecules of interest can be specifically labeled with radioactive atoms T or I4C and can be incorporated into substrates that also contain stable isotopes D, 15N and 180. 

In this chapter, we begin by describing the laboratory facilities and equipment needed for biochemical and molecular biological work. This is followed by advice on safe working in the laboratory, and discussion of the safety regulations that usually apply in a biochemistry laboratory. We describe a range of common laboratory activities, but do not include some important topics, such as chromatography, electrophoresis and photometric methods, which are considered later in specific chapters. The chapter concludes with a description of radioactive methods, and advice about alternatives to the use of radioactivity. 

Following this publication, Patrick et al. [59] reported a quantitative method using the combination of LC-MS/MS and radioactivity for the determination of ezetimibe in biological samples as well as the metabolite profiling of ezetimibe by. Similarly, Ghosal et al. [60] also applied the combination of LC-MS/MS and radioactivity to analyze ezetimibe and its metabolites. However, there were no details reported for validation of the analysis of both LC-MS/MS and radioactivity methods. 

Next, detection and quantitation of tumor cells adherent to specific substrates can be done by either radioactive or nonradioactive methods. For radioactive methods, labeling and detection has been already described in Section 2.3.3.5. Alternatively, tumor cells can also be labeled with fluorescent dyes, and quantitated accordingly (see same section). We will describe below only nonradioactive methods. 

A radioactive method has also been developed for determination of catalyst levels in reactors, hoppers, and catalyst-feed lines of moving-bed units (331). The equipment consists of one or more radiation sources (radium chloride), a Geiger tube, and associated electronic instruments. The radium sources are mounted within the vessel at intervals over the range of levels to be measured, with the Geiger tube at the top. The exact amounts and locations of the radium sources are so proportioned that radiation from each source is no longer detected when covered by a 2-ft. layer of catalyst. Thus the counter receives maximum radiation when the vessel is empty and decreasing intensities as catalyst level rises. 

Hatuda, Z., 1954. Radioactive method for geological exploration. Memoirs College Sci., Univ. Kyoto, Scr. B, 21, Art. 9 231-271. 

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