why not stay with room temp?
many structures have been solved at RT...
Mark J. van Raaij
Dpto de Bioquimica, Facultad de Farmacia
Universidad de Santiago
15782 Santiago de Compostela
Spain
http://web.usc.es/~vanraaij/researcherID: B-3678-2009
On 15 Dec 2009, at 13:20, Natalie Zhao wrote:
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Rafael Couñago
Sent: 14 December 2009 20:22
To: [log in to unmask]
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
--
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