Here's a method that has had some success in reducing mosaicity, either
with or without cryoprotectant:
Chae Un Kim, Raphael Kapfer and Sol M. Gruner (2005), High Pressure
Cooling of Protein Crystals without Cryoprotectants, ActaCryst. D61,
881-890
This method may be available at a synchrotron near you.
Cheers,
--
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With the single exception of Cornell, there is not a college in the
United States where truth has ever been a welcome guest - R.G. Ingersoll
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David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[EMAIL PROTECTED]
On Mon, 2007-07-09 at 18:05 -0400, Mary Fitzgerald wrote:
> Help please!
>
> I'm looking for some new ideas. I have crystals that come out of a
> sitting drop with a mixture of sodium cacodylate at pH 6.5, magnesium
> acetate and MPD for the well solution. The MPD concentration is
> sufficient to act as a cryoprotectant. Currently, I directly freeze
> these crystals in liquid nitrogen. When I collect data, I typically
> have high anisotropic mosaicity; it ranges from 0.8 to 1.2. This is
> further complicated with a weakly diffracting crystal (4-5 A) that has
> a long unit cell axis of ~500 and often twinning.
>
> It has been suggested to me that the cryoprotectent is a problem. I
> haven't checked the diffraction at room temperature, yet. Please no
> suggestions of finding a different crystal form as that's not a
> consideration at the moment. I have my reasons. I did find one
> crystal that has lower mosaicity (0.5 to 0.8) but had weaker
> diffraction then the typical crystal. Attempts at flash cryoannealing
> have not helped.
>
> So, what's a good way to change the cryoprotectant if the
> cryoprotectant is the precipitant? I've considered trying dehydration
> but wasn't certain if that would help with the mosaicity.
>
> Thanks for any ideas,
>
> Mary X. Fitzgerald
> Postdoctoral Associate
