Electron microscope

The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times.

Disadvantages

The samples have to be viewed in vacuum, as the molecules that make up air would scatter the electrons. This means that no living material can be studied. Recent advances have allowed samples to be imaged using lower vacuums and with partially hydrated samples, and the use of an electron transparent membrane between a biological sample and the vacuum has been shown to allow fully hydrated samples to be imaged, although there is a reduction in resolution.

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The samples have to be prepared in many ways to give proper detail, which may result in artifacts—objects that are purely the result of treatment. This gives the problem of distinguishing artifacts from material, particularly in biological samples.

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Electron microscopes image conductive or semi-conductive materials best. Non-conductive materials can sometimes be imaged by an electron microscope, however the electron beam will be absorbed by the material, which will change the physical properties of the material (for example, the material can burn off). A common preparation technique is to coat the sample with a several-nanometer layer of conductive material, such as gold, from a sputtering machine; however this process has the potential to disturb delicate samples.

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There have been a few scientists, such as Dr. Harold Hillman, who believe that such artifacts are responsible for all the structures observed in biological samples by electron microscopy, rendering the techniques useless for these materials. Mainstream scientists maintain that the results from various preparation techniques have been compared, and as there is no reason that they should all produce similar artifacts, it is therefore reasonable to believe that electron microscopy features correlate with living cells. In addition, higher resolution work has been directly compared to results from X-ray crystallography, providing independent confirmation of the validity of this technique. Recent work performed on unfixated, vitrified specimens has also been performed, further confirming the validity of this technique.

Related Topics:
Dr. Harold Hillman - X-ray crystallography

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Electron microscopes are also very expensive to buy and maintain.

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See :Category:Electron microscope images for images made with electron microscopes.

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