Ch. 9b: Electron Microscope

electron microscopy

higher velocity = lower wavelength of electrons

wavelength of electron beam is (greater or lower) than wavelength of visible light

lower

resolution of electron microscopy is (greater or lower) than light microscopy

greater

TEM

transmission electron microscopy

• sends a high beam of electron through a thin specimen

• electron scattering by stained areas

• monochrome

• looks at organelles

• sample preparation

TEM sample preparation

fixatives

• glutaraldehyde: crosslike proteins

• osmium tetroxide: fixes macromolecules with C=C

quick freezing, replaces ice with resin so can cut, add heavy metal to stain and see in EM

Immunogold EM

uses antibodies that carry gold beads

• visible in EM as black dots

• only labels surface antigen

• counterstain with heavy metals to highlight non-target cells

SEM

scanning electro microscopy

• gets 3D image of sample

• fixed, dehydrated sample

• surface of cells

sinle particle reconstructio

take pics of the same thing many times then combine to make 3D

• avoids specimen damage

CLEM

correlated light and electron microscope

• combines strengths of both microscopes at the same time

SEM

scanning electron microscopy

• region of interest imaged

SIM

structured illumination microscopy

• sample of interest located with fluorescent microscope

FIB-EM

focused ion beam-scanning em

• combined SEM with FIB for 3D image

• ion beam removes surface of specimen