-----Original Message----- From: owner-c...@dl.ac.uk [mailto:owner-c...@dl.ac.uk] On Behalf Of Rafael Couñago Sent: 14 December 2009 20:22 To: c...@ccp4.ac.uk Subject: [ccp4]: TDS upon flashcooling
Dear all, I got these beautiful looking crystals that grow in high salt (1.8M) and diffract under 2.0A at room temp. My attempts so far to cryo protect them have resulted in a loss of resolution (2.5A tops) and increased anisotropy. I have tried some of the usual suspects; no cryo, ethylene glycol, glycerol (even 5% makes my crystal crack), sucrose, glucose, paratone-n (no diffraction at all). I have tried both dipping the crystal straight into liquid nitrogen and flash cooling it in the cryostream. An interesting observation is that the diffraction pattern following freezing has a substantial amount of thermal diffuse scattering (but no ice rings). If I remove the crystal from the cryostream and re-anneal it at room temp (in air or in mother liquor or mother liquor + cryo) most of the TDS goes away, but the max resolution is still around 2.5A and the higher anisotropy is still there. Extending re-annealing times lead to cracking of the crystal. My two questions would be: - any thoughts on cryo solutions? - does the result from the re-annealing experiment ring any bells? Would this be an indication that I need the cooling to be faster or slower? Cheers, Rafael. -- Rafael Couñago Research Fellow Department of Biochemistry University of Otago 710 Cumberland St Dunedin, New Zealand ph: (03) 479 5148 -- Scanned by iCritical.
