Nisarg posted an Question
April 18, 2021 • 22:49 pm 30 points
  • Biotechnology (BT)

Can anyone please explain what is shadowing technique of staining in tem(transmission electron microscope)????

can anyone please explain what is shadowing technique of staining in TEM(transmission electron microscope)????

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    Krishan k jakhad best-answer

    Metal shadowing of bacteria, viruses, isolated molecular assemblies is another high resolution method for observing the ultrastructure of biological specimens. The actual procedure for producing a metal shadow is relatively simple; a heavy metal is evaporated from a source at an oblique angle to the specimen. The metal atoms pile up on the surfaces that face the source, but the surfaces away from the source are shielded and receive little metal deposit, creating a "shadow." ...However, many specimen preparation techniques that can precede metal shadowing, and all provide superior preservation in comparison to air drying, a required step in negative staining procedures.  negative case of transmission electron microscopy, opaqueness to electrons is related to the atomic number, i.e., the number of protons. Some suitable negative stains include ammonium molybdate, uranyl acetate, uranyl formate, phosphotungstic acid, osmium tetroxide, osmium ferricyanide and auroglucothionate. These have been chosen because they scatter electrons strongly and also adsorb to biological matter well.


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