Imaging with Waves
How good is the eye?
100 - 50 m resolution
Seeing small things
Antonie van Leeuwenhoek
The inverted telescope
Modern optical microscopy
Focusing down
Airy Disk
0.61•/NANA = n•sin
2
Resolution ~ 300 nm
The diffraction limit
Objects spaced apart by less than d~/2NA cannot be resolved individually!
Ernst Abbe (1840-1905)
Imaging with the diffraction limit
Object ImageFocal spot
Images can be improved by using shorter wavelengths
CD versus DVD
7x more data on DVD because of different wavelength!
780 nm 650 nm
(Blu-Ray DVD uses 405 nm, 6x more data than DVD)
Seeing single molecules at work
Seeing smaller thingsusing EM radiation using particles
of particles:
€
= hmv
Electron with v = 1.0 x 105 m/s:
€
=6.626 ×10−34 Js
9.11×10−31kg( ) 1.0 ×105m /s( )
€
€
=7.3×10−9m
€
=7.3nm
Electron Microscopy
Resolution ~ 0.2 nm
Electron Microscopy
Cryo-Electron Microscopy
Cryo-Electron Microscopy
Cryo-Electron Microscopy
Viral DNA portal protein
What are X -rays?
Wilhelm Conrad Röntgen (1845-1923)
Electromagnetic radiation with wavelength of ~10-10 m
Focusing or diffracting?
Bragg diffraction Diffraction pattern
2d sin = n
X-ray crystallography
Protein structure determination
X-ray crystallography reveals electron densities
Protein structure determination
No longer a mystery
No longer a mystery
DNA polymerase on the DNA backbone