Relative specific radioactivities

This complex reached a maximum of about 10% in the early stages of reduction and then decreased. Initially the relative specific radioactivity was 1.93 for methyl linoleate and zero for conjugated diene. Relative specific radioactivity in the products at 50% reduction was about equal in the monoene (1.0), stearate (0.96), and diene-Fe(CO)3 (1.0), but only minor in the free conjugated diene (0.14). Although the diene-Fe(CO)3 complex is a significant intermediate in the reduction of linoleate, the free conjugated diene is not. 

Table 4. Relative specific radioactivities in the products of formed from radioactive alkanes. ...

The proportion of glutamate in the small glutamate pool, i.e., the glial cells, can be estimated from the relative specific radioactivity of glutamine compared to glutamate after administration of group 1 precursors (acetate, aspartate, NaHCOj). In several re-... 

The pathway of the biosynthesis of Neu5Ac demonstrates the origin of sialic acids from the cellular hexose and hexosamine pools. These sugars are, therefore, suitable components for the study of the biosynthesis of sialic acid. However, only ManNAc has been shown to be a relatively specific precursor of sialic acids, as may be seen from the distribution of radioactivity between the individual monosaccharides of glycoconjugates after incubation. Injections of radioactive ManNAc into animals, or incubation of surviving tissue slices or individual cells with this compound, give incorporation of label mainly into the sialic acids.226 227... 

Cell-free systems provide a rapid and convenient method for preparing GA and GA-precursors with high specific radioactivity, although on a relatively small scale. [ C]-labeled ent-kaurenoid precursors of GAs have been obtained from [2- C] mevalonic acid by incubating with cell-free systems from endosperm of Marah macrocarpus (83) or Cucurblta maxima (84,85) ... 

In the fourth experiment incorporation of intermolecularly doubly labeled phenylalanine (at carboxyl carbon and at the / carbon of the side chain) was investigated. The labeled decodine and decinine contained radioactivity only at the expected four carbon atoms C-l, C-3, C-l 1, and C-13 which were isolated and assayed for radioactivity. The ratios of relative specific activities calculated from these data (C-3/C-1, C-11/C-l3) were in good agreement with the activity ratio of the precursor (C02H// -CH2). 

The importance of secondary-radiation effects may be seen from the decomposition of dextran-C sulfate containing about 20 D-glucose residues per molecule, observed by Bayly and Weigel. It had the relatively low specific radioactivity of 22.4 mC. per g.-atom of carbon (about 3 mC/ millimole of dextran sulfate). After three weeks in the freeze-dried form, it had charred and become a total loss. The decomposition was presumably attributable to a secondary-radiation effect arising from a prior liberation of sulfuric acid, which then released more sulfuric acid to destroy the material. 

All decay products, with their relatively short half-lives resulting in correspondingly high specific radioactivity (i.e., high numbers of decays per second and mass unit), are best identified and measured using alpha- and gamma-spectrometry (IAEA... 

Most transuranium elements - with their relatively short half-lives resulting in correspondingly high specific radioactivity (i.e.. 

Covalent protein binding studies require the use of radiolabeled compounds. H-tracers are often used because they are relatively easy to synthesize and are of high specific radioactivity. However, possibilities exist that the H-label may be lost if oxygenation of the test compound occurs directly on the carbons where the H-label is attached. As a consequence, observed binding values could be underestimated. tracers, on the contrary, are less likely to lose the label, and therefore are preferred. However, possibilities of losing a radiolabel should be considered for any given radiolabeled tracer. Therefore, evaluation of the loss of radiolabels needs to be performed before covalent... 

The loss of the hydroxyl group from either the starting cyclohexanol (to give cyclohexane), or from phenol (to give benzene) can also take place. Dehydration of cyclohexanol to cyclohexene is also possible as summarised in Scheme 3. These reactions were studied over various metal catalysts, by using different mixtures containing one labelled component. Typical results obtained on Cu, Ni and Pt catalysts are summarised in Table 5. The specific radioactivities decreased in the sequence cH-ol > cH-one > phenol on Cu and Ni catalysts, while a different order cH-ol > phenol > cH-one was observed on Pt, as well as on Pd. Thus, the sequential reaction 1 2 leads to phenol in the former two catalysts and the direct route to phenol lA is possible on Pt and Pd. The following relative rates were determined for Ni catalyst ... 

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