With salt-based conditions sodium malonate is your friend:
Acta Cryst D59: 2356
On Tue, 2009-12-15 at 12:20 +0000, 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
>
--
Edwin Pozharski, PhD, Assistant Professor
University of Maryland, Baltimore
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