Dear Saravanan,
Cryocooled crystals have relatively large mosaic spreads, on the order of tenths of degrees. On a lab source the smallest mosaicity you will see will be about 0.2 degrees which is actually the geometrical and spectral contribution from the instrument. On a typical synchrotron beamline the lowest measurable mosaicity may be much smaller dependent on the optics configuration.
Check out Bellamy, H. D., Snell, E. H., Lovelace, J., Pokross, M. and Borgstahl, G. E. O. "The High Mosaicity Illusion: Revealing the True Physical Characteristics of Macromolecular Crystals" Acta Cryst. D56, 986-995 (2000), or Snell, E. H., Bellamy, H. D., and Borgstahl, G. E. O. "Macromolecular Crystal Quality" Methods in Enzymology, Macromolecular Crystallography, Part C, editors C. Carter and B. Sweet 368, 268-288 (2003) for details on what can be achieved when the beamline is configured specifically to measure the crystal contribution to the mosaicity.
Protein crystals are surprisingly perfect and can have rocking widths comparable to solid state crystals, e.g. hundredths or even thousandths of a degree depending on the crystal. Measuring them is not trivial.
Cheers,
Eddie
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Edward Snell Ph.D.
CEO Hauptman-Woodward Medical Research Institute
Assistant Prof. Department of Structural Biology, University at Buffalo
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-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of pselvam
Sent: Tuesday, May 24, 2016 10:01 AM
To: [log in to unmask]
Subject: [ccp4bb] crystal mosaicity values
Dear CCP4 experts,
I am looking for mosaicity values for deposited PDBs. What would be the minimum or optimal mosaicity value one can obtain with good crystals?
Thanks in advance
Saravanan
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