Imaging with Waves

How good is the eye?

100 - 50 m resolution

Magnification

Seeing small things

Antonie van Leeuwenhoek

The inverted telescope

Robert Hooke

Seeing sharper

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)

UV lithography

Superresolution

Single molecules

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