Helen NguyenChem. 12B

Seminar PresentationSpring ‘05

1. History of crystallography_ Definition and Greek roots_ 1895, W.C.Roentgen_ 1912, Max von Laue

2. How does it work and what does it use for? _ Useful in phase identification _ Cover the enumeration of the symmetry patterns

3. Methods and diffraction patterns._ X-ray diffraction_ Electron diffraction

_ Neutron diffraction4. Determination of the first protein using crystallography

_ Myoglobin_The experiment_ Brag’s law

5. Advantage and disadvantage6. Elucidation relative stereochemistry.

• Method uses to study crystals.

• Crystallon-solid

• Graphein means write

• X-ray Diffraction

• Electron Diffraction

• Neutron Diffraction

http://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Sound

• 1895- W.C.Roentgen

• 1912- William Lawrence Bragg

• Determine the crystalline spacing for a number of substances.

• Collimated x-rays to diffract off of different crystal planes.

http://www.roentgenlauf.de/page5.php?lang=1

Roentgen

http://www.aip.org/history/esva/catalog/esva/Bragg_Lawrence.html

What is Electron Diffraction?

• By firing a beam of electrons at a sample and observe their deflection.

• The electrons are deflected as waves, as in classical diffraction. Restriction?

• Performing of crystal?• Scattered Electrons by…?• Limitation of penetration?• Transmission Electron Microscope (TEM).

http://en.wikipedia.org/wiki/Lattice

Neutron DiffractionNeutron Diffraction

• Determine the atomic structure of a material.• Found in the atomic nucleus. • All quantum particles can exhibit wave

phenomenaassociate with light or sound• Requirements• Interaction? Do not?• Reveal?• Neutrons v.s X-ray•

•Helium atom (schematic)Showing two protons (red), two neutrons (green) and two electrons (yellow).

http://en.wikipedia.org/wiki/Subatomic_particle

X-ray diffractionX-ray diffraction• Visualize the electron clouds around atoms.• Most important. Pattern?• Analyzing• The lattice is revealed• Bragg's law• Interact with the incoming X-ray photons to

diffract them• Myoglobin, Max Perutz and Sir John Cowdery

Kendrew

http://en.wikipedia.org/wiki/Diffraction

http://en.wikipedia.org/wiki/Myoglobin

How Brag’s law is usedHow Brag’s law is used

• X-rays hit an atom

• Make the electronic cloud move

• Rayleigh scattering/Re-radiate waves

• Constructive/destructive

http://en.wikipedia.org/wiki/Bragg%27s_law

An Experiment An Experiment Using X-ray DiffractionUsing X-ray Diffraction

• Study:a. how oxygen diffused within the protein b. how oxygen is finally released into the surrounding solvent

• Substitution of carbon dioxide• Advantage?/Trigger ligand released• The mutant L29F of myoglobin• Conformational changes/ first few hundred

picoseconds

Figure 1. 3D (left and center) and 2D (right) representations of the terpenoid, atisane. In the 3D model on the left, carbon atoms are represented by gray spheres, white spheres represent the hydrogen atoms and the cylinders represent the bonds. The model is enveloped in a "mesh" representation of the molecular surface, colored by areas of positive (red) and negative (blue) electric charge. In the 3D model (center), the light-blue spheres represent carbon atoms, the white spheres are hydrogen atoms, and the cylinders in between the atoms correspond to single-bonds.

http://en.wikipedia.org/wiki/Molecule

How does X-ray Diffraction How does X-ray Diffraction Apply to Current Days?Apply to Current Days?

• Used to determine how drugs, such as anti-cancer medications

• Molecule must be crystallized/why?

• Determine a structure/Paintaking?

• Diffractometer, a machine that emits a beam of x-rays

An X-ray picture (radiograph) taken by Röntgen

http://en.wikipedia.org/wiki/X-ray

X-ray Application Cont’X-ray Application Cont’

• Diffraction images

• What important?/Problem solving--- combination and computational methods

• A model made up of atoms is built and refined against the observed data

X-rays can reveal the details of bones and teeth

http://en.wikipedia.org/wiki/X-ray

ConclusionConclusion

• X-ray, Neutron, and Electron are the three diffraction methods

• X-ray is the method that determined the first protein molecule which is myoglobin by Max Perutz and Sir John Cowdery Kendrew with the use of Brag’s law.

• Today X-ray is used to determine how drugs, such as anti-cancer medications

Bibliography

• http://en.wikipedia.org/wiki/

• http://web.chem.ucla.edu/~harding/cfqpp/xray30.pdf

• http://www.answers.com/topic/x-ray-crystallography

• http://www.esrf.fr/UsersAndScience/Publications/Highlights/2003/Materials/MAT15/

• http://en.wikipedia.org/wiki/Atomic_nucleus

• http://en.wikipedia.org/wiki/Sound

• http://www.roentgenlauf.de/page5.php?lang=1

• http://www.aip.org/history/esva/catalog/esva/Bragg_Lawrence.html

• http://en.wikipedia.org/wiki/Lattice• http://en.wikipedia.org/wiki/Subatomic_particle

• http://en.wikipedia.org/wiki/Diffraction

• http://en.wikipedia.org/wiki/Myoglobin

• http://en.wikipedia.org/wiki/Bragg%27s_law

• http://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/X-ray