Re: [ccp4bb] PEG3350-based cryoprotectant

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: PEG3350-based cryoprotectant
From: Jürgen_Bosch jubosch {- at -} JHSPH {- dot -} EDU
Date: 2009-02-14

Next message:
Subject: Re: CCP4BB Digest - 12 Feb 2009 to 13 Feb 2009 (#2009-45)
From: Clemens Vonrhein vonrhein {- at -} GLOBALPHASING {- dot -} COM
Date: 2009-02-16

Subject: Re: PEG3350-based cryoprotectant
From: Tim Gruene tg {- at -} SHELX {- dot -} UNI-AC {- dot -} GWDG {- dot -} DE
Date: 2009-02-15

Did you check whether your drops shrink or grow after setting them up? If
your calculation is correct, they shoud grow. In that case you are growing
crystals be salting-in: As the salt concentration decreases as the
drop volume increases, the solubility curve of your protein drops faster
than its concentration so that it precipitates (fortunately in form of a
crystal).

If that's the case you final state is not what you probably think it is
and you are 'shocking' the crystal with a high concentration of all the
constituents of the buffer.

Aside from this: did you try to slowly increase the concentration of the
cryo-protectant rather than transferring the crystal directly into it? You
can achieve this with a pipette by slowly adding the cryoprotectant to
the crystal. - where 'slowly' can vary between seconds and minutes or even
hours.

Good luck, Tim

> I grow my crystals with vapor diffusion in 24-well format by hanging a drop
> of equal volume protein and precipitant solution over the reservoir of
> precipitant solution. Interestingly, when I do the math, the initial
> osmolarity of my drop is greater than that of the reservoir (due to the high
> NaCl in the protein solution). As far as I know, this runs against the
> principles of the vapor diffusion method, as vapor will leave the reservoir
> and enter the drop...
>
> Keith
>
>
> Department of Biochemistry & Molecular Pharmacology
> 970L Lazare Research Building
> University of Massachusetts Medical School
> 364 Plantation Street
> Worcester, MA 01605
>
--
Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen

GPG Key ID = A46BEE1A

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: PEG3350-based cryoprotectant
From: Jürgen_Bosch jubosch {- at -} JHSPH {- dot -} EDU
Date: 2009-02-14

Next message:
Subject: Re: CCP4BB Digest - 12 Feb 2009 to 13 Feb 2009 (#2009-45)
From: Clemens Vonrhein vonrhein {- at -} GLOBALPHASING {- dot -} COM
Date: 2009-02-16