CRISTALLOGRAFIA A RAGGI X Perche i raggi X

CRISTALLOGRAFIA A RAGGI X

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.

• 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.

Crystallization*

Crystallization Protein Crystal

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.

How Does X-Ray Crystallography Work ? – Image of diffraction

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.

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.

The Final Result ORIGX 2 ORIGX 3 SCALE 1 SCALE 2 SCALE 3 ATOM ATOM ATOM 1 2 3 4 5 6 7 8 9 10 11 0. 000000 0. 011173 0. 000000 N SER CA SER C SER O SER CB SER OG SER N ASP CA ASP C ASP O ASP CB ASP 1. 000000 0. 019585 0. 000000 A 1 A 1 A 1 A 2 A 2 A 2 0. 000000 1. 000000 0. 004858 0. 000000 0. 018039 21. 389 25. 406 21. 628 26. 691 20. 937 26. 944 21. 072 28. 079 21. 117 27. 770 22. 276 27. 925 20. 173 26. 028 19. 395 26. 125 20. 264 26. 214 19. 760 26. 575 18. 439 24. 914 0. 00000 -4. 628 -3. 983 -2. 679 -2. 093 -5. 002 -5. 861 -2. 163 -0. 949 0. 297 1. 371 -0. 856 1. 00 1. 00 A PDB coordinate file 23. 22 24. 42 24. 21 24. 97 28. 27 32. 61 21. 39 21. 57 20. 89 21. 49 22. 14 2 TRX 2 TRX 2 TRX 2 TRX 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162

The PDB http: //www. rcsb. org/pdb/