Structural Medicine     

Protein Crystallography Course



The only requirement for a protein crystal is that it diffracts. Diffraction depends on In other words, the size of a protein crystal doesn't tell you anything about how well it will diffract.

The First Shot

The diffraction quality of a crystal can vary with any combination of:

Strength of diffraction
Quality of diffraction
no diffraction multiple mosaic crystal
weak diffraction 10 angstroms mosaic crystal
promising diffraction 3.5-6 angstroms multiple crystal
good diffraction > 2.8 angstroms single crystal

Poor Crystals

How can you make a multiple mosaic crystal a single crystal?

How can you make weakly diffracting crystals diffract further? If none of the above work, find new conditions with higher precipitant concentrations.
See Enrico Stura's page.

Crystals for cryo-crystallography

Most data is collected at cryo temperatures because mounting crystals in loops is easier than mounting in capillaries and the cryo-temperatures reduce radiation damage.

If your crystals deteriorate within days or weeks of being grown, try "freeze and retrieve" (freezing your crystals in liquid nitrogen and storing them at 100K, then retrieving them for data collection)

It is usually best to grow your crystals in cryoprotectant. See a modified version of Elspeth Garman's protocol for cryoprotecting crystals.

Other links

After all the effort it takes to get crystals, it can be very tempting to collect poor data from poor crystals in the hope that any problems can be sorted out in data processing or even at structure solution. It is much more effective to spend the time sorting out the problems with the crystals instead.

Good Luck

© 1999-2005 Airlie J McCoy, University of Cambridge. All rights reserved.

Last updated: 24 December, 2006