Crystal
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102 m
2 m
2 mm

7 Crystal lattices
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http://www.xtal.iqfr.csic.es/Cristalografia/archivos_03/bravais-en.jpg
14 Bravais lattices

Symmetry – Space groups
2D symmetry
3D symmetry
Screw axis
Proteins are chiral – no mirror symmetry
Combination of Bravais lattices and symmetry operations leads to 230 possible space groups (not all
for proteins).

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http://people.mbi.ucla.edu/sawaya/m230d/Reduce/spacegroup.jpg
Example of space group information from International Crystallographic Tables

•Protein
•Big molecule
•Temperature sensitive
•Hundreds-thousands of rotating bonds
•Weak interactions mostly involved
•High solvent content (30-70 %)
•Fragile crystals
•Inorganic salt (ev. organics)
•Small molecule
•Thermostable
•None/few rotating bonds
•Strong (coulombic) interactions frequent
•Low/none solvent content
•Hard crystals

Phase diagram
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Protein crystallization techniques
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Protein crystallization by vapour diffusion: (a) microbatch, (b) sitting drop and (c,d) hanging
drop. In d and e, a sandwich is made of the mesophase (red) by placing a small glass coverslip
(hatched) (d) below or (e) above the bolus. From Nature Protocols
Protein crystallization by counter diffusion in capillaries.
Protein crystallization by dialysis.

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Various techniques = various path in the phase diagram


Automatization vs. manual work
q High-throughput
q
q Low volumes (20-150 nl)
q
q Reproducibility
q Individual design
q
q Immediate visual control
q
q Complex sample handling

Further reading
•http://journals.iucr.org/
•Naomi E. Chayen: Protein Crystallization Strategies for Structural Genomics, 2007
•Terese M. Bergfors: Protein Crystallization, 2009
•Alexander McPherson: Introduction to Macromolecular Crystallography, 2011
•etc.
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