* Tritium (³H): A hydrogen isotope often used to label proteins by replacing regular hydrogen atoms in amino acids. Its relatively long half-life and ability to be incorporated into organic molecules make it useful for labeling experiments.
* Carbon-14 (¹⁴C): Similar to tritium, it can be incorporated into the backbone of amino acids during protein synthesis. It has a longer half-life than tritium, making it suitable for longer-term studies.
* Sulfur-35 (³⁵S): Often used to label proteins containing the amino acid methionine, as it is incorporated into its side chain. It has a moderate half-life and emits a beta particle that can be easily detected.
* Iodine-125 (¹²⁵I): Used to label proteins by attaching it to tyrosine residues. It emits gamma radiation, making it suitable for imaging and detecting proteins in vivo.
The choice of radioactive isotope depends on the specific experiment and the type of protein being studied. Factors such as the half-life, radiation type, and ease of incorporation into the protein need to be considered.
Remember that working with radioactive isotopes requires strict safety protocols and proper disposal.
