Key Concepts of Section 4.3

• Electron microscopy provides very high-resolution images because of the short wavelength of the high-energy electrons used to image the sample.

• Simple specimens, such as proteins or viruses, can be negatively stained or shadowed with heavy metals for examination in a transmission electron microscope (TEM).

• Thicker sections generally must be fixed, dehydrated, embedded in plastic, sectioned, and then stained with electron-dense heavy metals before viewing by TEM.

• Specific proteins can be localized by TEM by employing specific antibodies associated with a heavy metal marker, such as small gold particles.

• Cryoelectron microscopy allows examination of hydrated, unfixed, and unstained biological specimens in the TEM by maintaining them at very low temperatures.

• Scanning electron microscopy (SEM) of metal-shadowed material reveals the surface features of specimens.