Autoradiography

Autoradiography is a biochemical technique that uses radioisotopes to visualize the distribution of a substance within a biological specimen. The method involves the exposure of a radioactive sample to a photographic film or detector, which captures the pattern of radioactivity. Autoradiography is widely used in molecular biology, cell biology, and histology to study the localization and quantification of proteins, nucleic acids, and other molecules.

Principles

Autoradiography relies on the emission of beta particles or gamma rays from radioactively labeled molecules within a sample. When these particles strike a photographic film or other sensitive surface, they create an image that corresponds to the distribution of the labeled compound. The intensity of the image reflects the concentration of the radioactive material, allowing for both qualitative and quantitative analysis.

Applications

1. 1. 1. Molecular Biology

In molecular biology, autoradiography is often used to detect the presence of specific DNA or RNA sequences on blots (e.g., Southern or Northern blots). It is also essential in the sequencing of DNA, where it helps visualize fragments that have been separated by gel electrophoresis.

1. 1. 1. Cell Biology

In cell biology, autoradiography can identify the distribution of various molecules within cells or tissues. It is particularly useful in studying receptor binding and the localization of drugs within cells.

1. 1. 1. Histology

Histology utilizes autoradiography to examine the uptake of labeled compounds in different tissues, providing insights into metabolism and the functioning of various organs.

Techniques

1. 1. 1. Wet Autoradiography

This involves placing the photographic film in direct contact with the wet sample, which is typically kept at low temperatures to prevent decay of the tissue and the radiolabel.

1. 1. 1. Dry Autoradiography

Dry autoradiography does not require the sample to be in a wet state and is suitable for longer exposure times, allowing for the detection of lower levels of radioactivity.

1. 1. 1. Microautoradiography

Microautoradiography is a technique used for examining very small samples, including sections of tissues at the microscopic level. It provides high-resolution images that help in the detailed study of the distribution of molecules.

Safety and Limitations

Handling radioactive materials requires stringent safety measures to prevent exposure to harmful radiation. Autoradiography also has limitations in resolution, and the decay of radioactive isotopes can complicate long-term studies.

See Also

• Radioisotope
• Beta particle
• Gamma ray
• Molecular biology
• Cell biology
• Histology