10. autoradiography. x - ray crystallography

autoradiography

Autoradiography is a technique used to visualize molecules or fragments of molecules that have been radioactively labeled.

Amino acids or nucleotides can be labeled with radioactive isotopes, which are incorporated into their molecular structure. These labeled molecules emit weak radiation from the regions where they are localized.

The cells or tissue sections containing the labeled molecules are coated with photographic emulsion, which contains silver bromide crystals that act as detectors for the radiation.

Photographic development of the slides reveals the location of the radioactive molecules as dark grains, indicating where the radiation was emitted.

x ray crystallography

X-ray crystallography is a key method used to determine the arrangement of atoms and the molecular structure of crystals. It is the most favored technique for structure determination of proteins and has been crucial in visualizing the structures of molecules such as proteins, cholesterol, vitamin B12, hemoglobin, and myoglobin.

In the process, a crystallized sample of the target substance is mounted in the crystallography machine and illuminated with an X-ray beam. The X-rays are scattered by the electrons in the crystal, creating a diffraction pattern.

This diffraction pattern is analyzed to create a 3D electron density map, which is used to construct a 3D model of the molecule, revealing the arrangement of atoms.

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