Retrovirus, Ultrathin Section and TEM


Transmission electron microscopy (TEM) involves a high voltage electron beam emitted by a cathode and formed by magnetic lenses. The electron beam that has been partially transmitted through the very thin (and so semitransparent for electrons) specimen carries information about the structure of the specimen. The spatial variation in this information (the "image") is then magnified by a series of magnetic lenses until it is recorded by hitting a fluorescent screen, photographic plate, or light sensitive sensor such as a CCD (charge-coupled device) camera. The image detected by the CCD may be displayed in real time on a monitor or computer. Transmission electron microscopes produce two-dimensional, black and white images.

A Transmission Electron Microscope has magnification and resolution capabilities that are over a thousand times beyond that offered by the light microscope. With the introduction of aberration-corrected electron lenses, both the spatial resolution and the image quality in transmission electron microscopy have been significantly improved and resolution below 0.5 ångströms has been demonstrated. In the life sciences, it is still mainly the specimen preparation which limits the resolution of what we can see in the electron microscope, rather than the microscope itself. TEM continues to play a critical role in discovering and describing new organisms, especially viruses.

Bozzola JJ, Russell LD (1999). Electron Biology Principles and techniques for Biologist, Sudbury, MA: Jones & Bartlett Learning.

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