ELECTRON MI-CROSCOPY

LESSON 5

TYPES OF MICROSCOPY

Light Microscopy Bright-field microscopy Phase Contrast microscopy Differential Interference Contrast (or Nomarski) Dark-field microscopy Fluorescence microscopy Confocal Scanning microscopy

Electron Microscopy Transmission electron microscope (TEM) Scanning electron microscope (SEM)

Learning Resources

1. Junqueira’s Basic Histology ; pp 7 & 9

2. Looking at the Structure of Cells in the Microscope

http://www.ncbi.nlm.nih.gov/books/NBK26880/#A1749▪ The Electron Microscope Resolves the Fine

Structure of the Cell.▪ Images of Surfaces Can Be Obtained by Scanning

Electron Microscopy▪ Metal Shadowing Allows Surface Features to Be

Examined at High Resolution by Transmission Electron Microscopy

▪ Freeze-Fracture and Freeze-Etch Electron Mi-croscopy Provide Views of Surfaces Inside the Cell

Resolution, resolution!!!

Electron Microscopy

Why electron beams? The wavelength, much shorter than of light

Types Transmission electron microscope (TEM) Scanning electron microscope (SEM) - sur-

face contoursTEM SEM

R = 0.61λ/ N.A.

Electromagnetic lenses

• a coil of wire through which current flows• magnetic field in the center.• electrons traveling in their path down the central

hole.

TEM

Dark (Electron dense)

(Electron transparent)

Bright (Electron lucent)

Contrast in TEM

• Bright (Electron lucent) - electrons readily passed

• Dark (Electron dense) - electrons absorbed

Transmission electron microscope (TEM)

SEM TEMDIC

SEM

Scanning electron microscope (SEM)

Metal Shadow-ing

• high resolution three-dimen-sional replica of the specimen

• heavy metal shadowing of bacteria to demonstrate flagella

Freezing Techniques

•Freeze-Fracture •Freeze-Etch

TEM Section and Freeze Fracture