1. (X-Ray Crystallography) X-RAY DIFFRACTION

2. I. X-Ray Diffraction  Uses X-Rays to identify the arrangement of atoms, molecules, or ions within a crystalline solid  Quantitative and qualitative Ooi, L. Principles of X-ray Crystallography (2010)

3. A. X-Rays  0.1 – 100 Angstroms (Å)  Useful Range: 0.5 – 2.5 Å

4. B. Amorphous Substances 1. Gases and Liquids  Extremely difficult 2. Non-crystalline Solids  Atoms are not regularly arranged or regularly shaped  Interference  Fiber Diffraction

5.  Atoms are regularly arranged  “The Unit Cell” – a cookie cutter C. Crystalline Solids Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)

6. II. X-Ray Crystallography A. Small-molecule crystallography  Up to ~100 atoms  Organic molecules, catalysts, newly synthesized drugs, etc.  Identify each atom B. Macromolecular (protein) crystallography  Large biological molecules – nucleic acids and proteins  Identify 2° structure Note: must show that the crystal structure (asymmetric unit) is comparable to structure in solution (biological unit)

7. III. X-Ray Diffractometer Ooi, L. Principles of X-ray Crystallography (2010)

8. A. X-Ray Source Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006) 1. X-Ray Tube (a) 2. Rotating Anode (b)

9. 3. Particle Storage Ring (Synchrotron Radiation)  Particle Accelerator Ooi, L. Principles of X-ray Crystallography (2010)

10. Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)  National Synchrotron Light Source at Brookhaven National Lab (Long Island)

11. B. Collimator  Narrow metal tube that selects and reflects the X-Rays into parallel paths Ooi, L. Principles of X-ray Crystallography (2010)

12. C. Crystal (Sample) Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006) 1. Growth – Screens  Crystal vs. useless blob 2. Optimization  Quantity 3. Crystal Quality  Purity 4. Mount for Data Collection  Cryocrystallography Note: Diffracted in “mother liquor”

13. D. Camera Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)  Goniometer  Goniostat

14. Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)

15. E. Detector Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006) 1. Charged Couple Device (CCD) 2. Image Plate (IP)

16. IV. Data Analysis  Measure intensity and position of diffracted X-Rays  Intensity: strength of diffracted beam  Position: direction in which beam was diffracted by the crystal Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)

17. Ooi, L. Principles of X-ray Crystallography (2010) Computer calculates this data from the diffraction pattern

18. A. Fournier Sum  Based on simple waves  f(x) = F cos 2π (hx + α)  F = f 0 + f 1 + f 2 + … Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)

19. B. Bragg’s Law  States: diffraction spots occur when 2 d sin θ = n λ Rhodes, G. Crystallography Made Crystal Clear, 3 rd ed. (2006)

22.  Molecular structure in solid crystalline state with extreme certainty  Direct inference of data  Provides limitless info.  Crystals  Slow  Hydrogen  Still just a model Benefits Downfalls