Cryo-EM and X-Ray Crystallography: Complementary or Alternative Techniques?

Giuseppe Zanotti
 

Abstract

Since its virtual establishment in 1912 with the first diffraction photograph from a crystal of copper sulfate [1], X-ray crystallography has been a tremendously invaluable tool in understanding not only the chemical nature of crystals, but also the three-dimensional structure of molecules. The latter is testified in the Cambridge Structural Data Base (CSD, http://www.ccdc.cam.ac.uk) with more than 800,000 structures deposited, and by the Protein Data Bank (PDB, http://www.rcsb.org/pdb), that nowadays count the structure of more than 120,000 biological macromolecules. The application of crystallography to life sciences has played a fundamental role in the field, in particular in biochemistry and in molecular biology, where the knowledge of the structure of macromolecules at atomic or nearly-atomic resolution allows to interpret the mechanisms underneath the biological processes in terms of the disposition of atoms in space. It is impossible in this short space to list even part of the achievements of structural biology that has taken place since the ’60, when the structures of the first proteins became available [2], to the present times.

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