[ccp4bb]: Crystals Crack in Cryo !!

[raji <raji@lamar.colostate.edu>]

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Dear Everyone,
I am working with a mutant of my WT molecule. It crystallizes in similar 
conditions as WT. However, when my crystals are soaked in the same cryo as 
that of WT, the crystals develop cracks. These cracked crystals diffract to 
about 3.5 Ang. Although seemingly fine at indexing and scaling stage), MR 
attempts with such data have failed.
The normal cryosoak involves stepwise soaking for a few mins. in increasing 
concentrations of MPD solution (final 24% MPD). I have tried varying final 
concentrations and times of soak in MPD at each step. In all these cases, the 
crystals develop cracks in a few hours. 
I also screened for various alternate cryoprotectants; in any other cryo, my 
crytals completely lose diffraction - they are essential "dead" for 
diffraction.
Does anyone have any suggestions/clues as to how I should handle this issue?
Thanks very much,
Raji

Rajeswari Edayathumangalam
Dept. of Biochemistry & Molecular Biology
Colorado State University
Fort Collins, CO 80523 USA