Hi Peter,
Isopropanol evaporates very quickly and crystals easily crack upon transfer between drops during cryoprotection. In our case a trick improved a diffraction limit from of about 4 to 1.2 A. We prepared reservoir solution with two times higher cryoprotectant concentration. A drop of this solution with a matching volume was placed near the crystallization drop containing the selected crystal and the two drops were joined and mixed with a mounting loop and vitrified.
Best regards,
Krzysztof
-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Peter Hsu
Sent: Friday, September 04, 2015 3:24 AM
To: [log in to unmask]
Subject: [ccp4bb] Isopropanol alternatives
Hi all,
I recently crystallized a protein in a condition containing isopropanol as the precipitant. After much optimization (additives, various cryoprotectants, etc), crystals still diffract to no better than 7A. I've been considering if I can change isopropanol to another precipitant, maybe ethanol? Was wondering if anyone in the community has any experience with doing this, and if so should I be using a similar range in concentration or screen more broadly? Has it helped anyone with diffraction?
Thanks in advance for any insight,
Peter
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