Radioisotopes in Molecular Biology
Published Online: 15 SEP 2006
Copyright © 2006 Wiley-VCH Verlag GmbH & Co. KGaA
Encyclopedia of Molecular Cell Biology and Molecular Medicine
How to Cite
James Slater, R. 2006. Radioisotopes in Molecular Biology. Encyclopedia of Molecular Cell Biology and Molecular Medicine. .
- Published Online: 15 SEP 2006
Radioisotopes are used extensively in molecular biology. They can be incorporated into DNA, RNA, and protein molecules, both in vivo and in vitro. As a consequence, the presence or metabolism of macromolecules can be investigated or “traced.” The incorporation of radioisotopes allows the detection of minute quantities, thereby facilitating experimental techniques that require high sensitivity. Labeling in vitro is much more efficient than labeling in vivo; specific activities regularly reach 108–109 dpm μ g−1 for in vitro 32P–labeling of DNA, for example. High-specific activity leads to greater sensitivity. Specific activity is inversely related to the half-life of the radioisotope. Low-energy emitters, such as 3H and 35S provide high resolution in autoradiography. High-energy, high-specific activity emitters such as 32P for nucleic acid labeling, provide great sensitivity but low resolution in autoradiography. The radionuclides 3H, 14C, 35S, and 125I are most commonly used for protein labeling; 32P and 33P are most commonly used for nucleic acid labeling.
- Specific Activity