1. CRISTALLOGRAFIA
A RAGGI X

2. Perche’ i raggi X?
Per vedere un oggetto le sue dimensioni devono essere almeno la meta’ della lunghezza d’onda della luce usata per rivelarlo.

3. The wavelength of visible light is far from small enough to see an atom, it is far to big. X-Rays have short enough wavelengths to “see” the atoms and the molecular structure of molecules.

4. Crystallization*

6. Crystallization
Protein Crystal

7. The Setup:
X-ray Source: x-ray tubes, rotating anode tubes, or particle storage rings
Gonoimeter
Detectors: X-ray films, CCD cameras, or Multiwire detectors.
CHESS at Cornell is an example of a particle storage ring.
Usually produce X-rays by bombarding Cu or Mb with electrons produced by a heated filament and accelerated in an electric field.
When electron knocked out of low energy level, another falls and fills its space, emitting and x-ray photon.
Multiwire detectors are lots of anode and cathode wires crisscrossing that pick up the x-ray signal.
CCD camera set up so x-rays hit a phosphor face plate which then emits photons picked up by an optical detector.

8. How Does X-Ray Crystallography Work ?
Image of diffraction

11. From diffraction to electron density map
Fourier Transform
To get from the diffraction pattern to the electron density, you have to use a Fourier Transform.
A transform is an eqn that transforms a function with some variables into a function with reciprocal variables. It is a way of going from the reciprocal lattice to the real lattice.

13. Resolution Resolution: another measure of how good your model is.
Resolution gives the size of the smallest molecule you can see or resolve.
Dependent on the amount of data ultimately phased and used in structure determination.

14. The Final Result A PDB coordinate file
ORIGX TRX 147
ORIGX TRX 148
SCALE TRX 149
SCALE TRX 150
SCALE TRX 151
ATOM N SER A TRX 152
ATOM CA SER A TRX 153
ATOM C SER A TRX 154
ATOM O SER A TRX 155
ATOM CB SER A TRX 156
ATOM OG SER A TRX 157
ATOM N ASP A TRX 158
ATOM CA ASP A TRX 159
ATOM C ASP A TRX 160
ATOM O ASP A TRX 161
ATOM CB ASP A TRX 162
A PDB coordinate file

15. The PDB