Re: [ccp4bb] cracking crystal

[Roger Rowlett]

We have had very good success with fragile, crack-prone crystals by doing gradual soaks in increasing glucose. Besides the osmotic pressure/solvent composition changes induced by cryopreservation, another reason crystals crack is drop dehydration. You can minimize dehydration of exposed drops by carrying out transfers in the cold room (I hate that, but it sometimes works), or by replacing coverslips over the well to maintain humidity. The most gentle method we use is our "no-fail" cryoprotection procotol, which you can find at: http://capsicum.colgate.edu/chwiki/tiki-index.php?page=Mounting+Protein+Crystals#No_fail_cryoprotection We have successfuly cryopreserved crystals that could not be frozen any other way. Fengxia Liu wrote: Dear All,   Could you please help me solve this problem?   I have a sensitive crystal, the mother liquor is 10% PEG4k+ 100 mM Tris-buffer pH 8.5, crystal is big and good but very sensitive, when i put it in cryoprotectants, cracking happened. First i used artificial mother liquor + 25% v/v glycerol, slowly decrease to + 12.5% v/v glycerol, all crystals cracked after immersed, finally i tried 50% mineral oil + 50% paratone, it still cracked (4- 5 cracks, but not broken) . even this cracked crystal can give me 3.2 angstrom diffraction, so no cracked crystal might give me 2.0+ angstrom diffraction. Now i don't have many crystals to try so many cryoprotectants, so anybody has experience on this? any suggestion would be greatly appreciated.   Thank you. Fengxiale -- Roger S. Rowlett Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: rrowl...@colgate.edu