...and I prefer to use PFPE (perfluoropolyether, trade name FOMBLIN) as an oil since it is less viscous, has no reactivity and is a low temp lubricant that freezes easily. Small molecule crystallographers have used it for years.
Kris --------------------------------- Kris F. Tesh, Ph D Director, Macromolecular Products Rigaku Americas Corporation 9009 New Trails Drive The Woodlands, TX 77381 USA 001 281 362 2300 x 144 From: Leonard Thomas <lmtho...@ou.edu> To: CCP4BB@JISCMAIL.AC.UK Date: 09/01/2009 10:09 AM Subject: Re: [ccp4bb] cracking crystal One thing that I have had work in the past is just increase the percentage of PEG. I think something around 30-35% may work for PEG4K, maybe a little higher. Most PEGS will work as a cryo protectant if the concentration is high enough. Also as mentioned before you could try stepping up the glycerol concentration very gradually. I had a colleague who said the protein he worked on in grad school had to be stepped up 1% increments or it would crack and fall apart. IIRC he had better then 2.0 ang. data for the final structure. Leonard Thomas Ph.D. Macromolecular Crystallography Laboratory Manager University of Oklahoma Department of Chemistry and Biochemistry 620 Parrington Oval Norman, OK 73019 lmtho...@ou.edu http://barlywine.chem.ou.edu Office: (405)325-1126 Lab: (405)325-7571 On Sep 1, 2009, at 5:25 AM, 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
