One thing to do here is to work out where you have your problem.
Is the crystal mosaic after you have introduced your potential cryo solutions, but still at room temperature? If it is, there is very little chance (snowballs in hell type chance) that it will get less mosaic when you flash cool it.
Can you transfer your crystal from the high AmPO4 to high AmSO4 ? or LiSO4 or malonate (all known cryo-salts) and flash cool from there?
Janet
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From: CCP4 bulletin board [[log in to unmask]] On Behalf Of ycheng [[log in to unmask]]
Sent: 08 October 2009 07:54
To: [log in to unmask]
Subject: [ccp4bb] Questions about cryoprotectant
Hi,
I am trying to find an appropriate cryo-condition for my protein crystals.
The mother liquid is 2-2.5M Ammonium phosphate dibasic
100mM TrisHCL pH8. The room-temperature diffraction looks not bad
(mosaicity 0.8, resolution 2.6) But the diffraction turned to be very
mosaic if I freeze the crytals in the absence of cryos or in the presence
of mother liquid plus different concentration of glycerol (5%,10%,15%.20%).
I don't think the ice formation is the problem since I didn't see any ice
by my eyes or ice diffraction in the presence or absence of cryos. Also, I
didn't see any cracks on my crystals when I transfered them to the cryo
conditions I have already tried.
My question here is:
1)what's the role of cryo? I know it helps prevent ice formation. Based on
my case, it looks like cryo might also help to keep the crytal packing good
when frozed.
2) What do I need to do to find a good cryo? What in my mind is to try
other cryos like sucrose, PEG400, ethylene glycol.
Thanks a lot for your attention!
Yuan
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