Erice Summer School June 10 2006

1
Erice Summer SchoolJune 10 2006
Session I

• Introduction
• Wah Chiu
• Baylor College of Medicine
• wah_at_bcm.edu

2
Rationales in Using Cryo-EM

• Can provide direct phasing from images
• Does not necessarily require crystals
• Can work with specimens at defined chemical or
  physiological conditions
• Can work with conformationally heterogeneous
  specimens
• Can provide initial model for crystallographic
  structure determination of a large complex

3
Hurdles in Cryo-EM

• Specimen preparation
• Electron radiation damage
• Low signal to noise image data
• Image correction is necessary
• Cryo-EM structure generally is low resolution
  compared to crystal structure

4
Achievements in Biological Cryo-EM

• 2-D monolayer protein crystal 3.5 - 1.9 Å
• polypeptide traced, water and lipid seen

• Helical array 9 - 4 Å
• Protein fold recognized

• Single particle 9 4.5 Å
• ? helices and ß strands visualized

• Large Assembly or whole cell 100 - 40 Å
• identify subcellular components

5
Pipeline in Cryo-EM
cryo-em sample preparation
biochemical preparation
imaging
data collection
annotation
image processing
reconstruction
structural analysis
6
Structures Solved by Cryo-EM
From M Baker