re : Paratone-N oil. 1) I find it much easier to work with if you cut it 50:50 with light mineral oil.
2) he stress of moving mechanically weak crystals (needles or thin plates) from a crystallisation liquor to the more viscous Paratone can cause the crystal to visibly bend - which might not be such a good thing. But I find that paratone works really well for most chunky, solid crystals. re: the high mosiacity issues - maybe you could try some gentle dehydration of the crystals? Maybe preincubate the crystals in mother liquor + 10>20% PEG20k prior to freezing? HTH Dave 2009/10/7 Janet Newman <[email protected]>: > 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 > ________________________________________ > From: CCP4 bulletin board [[email protected]] On Behalf Of ycheng > [[email protected]] > Sent: 08 October 2009 07:54 > To: [email protected] > 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 > -- ============================ Science knows it doesn't know everything...otherwise it would stop. - Dara O'Briain ============================ David C. Briggs PhD Father & Crystallographer http://drdavidcbriggs.googlepages.com/home Skype: DocDCB ============================
