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X Ray Diffraction Spectroscopy

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  • Light and its nature have caused a lot of ink to flow during these last decades. Its dual behavior is partly explained by (1)Double-slit experiment of Thomas Young - who represents the photon’s motion as a wave - and also by (2)the Photoelectric effect in which the photon is considered as a particle. A Revolution: SALEH THEORY solves this ambiguity and this difficulty presenting a three-dimensional trajectory for the photon's motion and a new formula to calculate its energy. More information on :
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X Ray Diffraction Spectroscopy

  2. 2. Discovery of X- rays by Rontgen in 1895 X- rays: EMR ,short wavelength, produced by electron transition of e- inner orbital of atoms. 0.01 to 10 nm, 0.08- 0.2 nm most useful.
  3. 3. X-ray generated by X-ray tube (bombardment of metal target) Radioisotopes Secondary fluorescent sources
  4. 4. X-ray Tube
  5. 5. X-ray Diffraction BRAGG’S Law for X-ray diffraction
  6. 6. 7 Bragg Equation where, d is the spacing of the planes and n is the order of diffraction. • Bragg reflection can only occur for wavelength The diffracted beams (reflections) from any set of lattice planes can only occur at particular angles predicted by the Bragg law.  nd sin2 dn 2
  7. 7. Diffraction Condition • The diffracted beams are found to occur when the reflections from planes of atoms interfere constructively. • When path difference is equal to wavelength.
  9. 9. X-RAY DIFFRACTION METHODS X-Ray Diffraction Method Laue Rotating Crystal Powder Orientation Single Crystal Polychromatic Beam Fixed Angle Lattice constant Single Crystal Monochromatic Beam Variable Angle Lattice Parameters Polycrystal (powdered) Monochromatic Beam Variable Angle
  10. 10. Rotating crystal method
  11. 11. 12 ROTATING CRYSTAL METHOD  In the rotating crystal method, a single crystal is mounted with an axis normal to a monochromatic x-ray beam. A cylindrical film is placed around it and the crystal is rotated about the chosen axis.  As the crystal rotates, sets of lattice planes will at some point make the correct Bragg angle for the monochromatic incident beam, and at that point a diffracted beam will be formed.
  12. 12. Structure of DNA This X-ray crystallography image of DNA shows a pair of strong arcs along the vertical axis. Such pictures gave Rosalind Franklin clues about the double helix structure of DNA, but they do not reveal the interactions between the crystallized protein and other molecules.
  13. 13. Performing X-Ray Diffraction
  14. 14. Application of XRD XRD is a nondestructive technique. Some of the uses of x-ray diffraction are; • Application in pharmaceuticals. • Application in determination of protein structure.
  15. 15. Advantages and disadvantages of X-rays Advantages; • X-ray is the cheapest, the most convenient and widely used method. • X-rays are not absorbed very much by air, so the specimen need not be in an evacuated chamber. Disadvantage; • They do not interact very strongly with lighter elements.
  16. 16. References D.Skoog,F.Holler,S.Crouch,Instrumental analysis, 2008,Cengage Learning India pvt.Lt,pg:344 -359,367-370 K.Wilson,J.Walker,Practical biochemistry: principles and Techniques,cambridge university press, 5th edition. Clive whiston,1987,X-Ray methods: Analytical chemistry by Open learning, British library,pg:1-29 Upadhya,Upadhya,nath,Biophysical chemistry:Principles and techniques,2003,Himalaya publishing house,3rd edition. pg:293-298
  17. 17. Park DJ, Choi Y, Heo S, Cho SY, Jin HJ, Bacterial cellulose nanocrystals-embedded silk nanofibers, 2012 Jul;12(7):6139-44. PMID: 22966722,Pubmed,NCBI. Zhang M, Song F, Wang XL,WangYZ,Development of soy protein isolate/waterborne polyurethane blend films with improved properties Colloids Surf B Biointerfaces. 2012 Dec 1;100:16-21. Epub 2012 Jun 7, PMID: 22766279 [PubMed],NCBI.
  18. 18. ExperimentalMethodsinStructuralBiology /protein-crystallography.html.