Radioactive Isotopes as Indicators in Biology.

Development of an 18F-Labeled Irreversible Inhibitor of Transglutaminase 2 as Radiometric Tool for Quantitative Expression Profiling in Cells and Tissues

“…Therefore, the biochemical process under investigation will not be influenced by the presence of the probe molecule. 13 Furthermore, considering that the radiolabel will consist of only one atom, the molecular properties of the original inhibitor will only be minimally influenced, provided that the radionuclide can be covalently attached to the molecule. Despite these advantages, radiolabeled activity-based probes are only scarcely reported.…”

“…Reporter groups that overcome these shortcomings can be obtained by labeling with radionuclides as the ionizing radiation that is emitted during their transformation into stable nuclides can be detected in a highly sensitive manner, which even allows their use in substoichiometric amounts in accordance with de Hevesy’s radiotracer principle. Therefore, the biochemical process under investigation will not be influenced by the presence of the probe molecule . Furthermore, considering that the radiolabel will consist of only one atom, the molecular properties of the original inhibitor will only be minimally influenced, provided that the radionuclide can be covalently attached to the molecule.…”

Transport of Ions Across Cellular Membranes

“…In the case of phosphate transport, for example, it is easy to imagine a formation of a phosphate ester at one boundary of a cell membrane and the splitting of the ester at another point in the cell. As a matter of fact there is some evidence that phosphate is actually taken up in muscle cells by beingesterified with glucose (126).…”

Biochemical Analysis

“…In spite of the weak radiation which makes assay difficult, this isotope is far easier to use than the heavy stable isotope C13, or the short half-life C11 which yields a considerably more energetic emission. Other isotopes which have great importance in general biochemical studies are P32 (47,72,166,256) and S35 (144,166), both of which are readily assayed. P32 is highly significant because of the wide chemical distribution of phosphorus in the proteins, nucleic acid (143), phospholipides (61), and phosphate esters of carbohydrates and their metabolic products.…”