Re: [ccp4bb] Help with reducing crystal mosaicity

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

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Subject: Re: Help with reducing crystal mosaicity
From: mesters mesters {- at -} BIOCHEM {- dot -} UNI-LUEBECK {- dot -} DE
Date: 2007-07-10

Mary,

freezing habitually increases mosaicity. In your case, the high water
content adds to the problem.
Try not to freeze the crystal but collect at sub-zero temperature (in
short glass capillaries or use oil plugs instead).
You have to optimize the "close to freezing" data-collection temperature.

I collected complete synchrotron datasets (of GCPII in buffer with
PEG1500 and PEG400) at 260-263 Kelvin which resulted in mosaicity values
of as small as 0.07 degrees! At 277 K, the crystals only last for a few
images and freezing did not work (for the buffer mentioned before).

- J. -

> -----Original Message-----
> From: Mary Fitzgerald
> Date: Mon, 9 Jul 2007 18:05:10
> To:CCP4BB@JISCMAIL.AC.UK
> Subject: [ccp4bb] Help with reducing crystal mosaicity
>
> 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
>

--
Jeroen Raymundus Mesters, Ph.D.
Institut fuer Biochemie, Universitaet zu Luebeck
Zentrum fuer Medizinische Struktur und Zellbiologie
Ratzeburger Allee 160, D-23538 Luebeck
Tel: +49-451-5004070, Fax: +49-451-5004068
E-mail: mesters@biochem.uni-luebeck.de
Http://www.biochem.uni-luebeck.de
Http://www.iobcr.org
Http://www.opticryst.org
--
If you can look into the seeds of time and say
which grain will grow and which will not - speak then to me (Macbeth)
--

CCP4bb navigation

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

Previous message:
Subject: Re: Proper Reference for Phil Evans Program POINTLESS
From: Phil Evans pre {- at -} MRC-LMB {- dot -} CAM {- dot -} AC {- dot -} UK
Date: 2007-07-10

Next message:
Subject: Post Doc on Hsp90-Complexes at ICR, London
From: Laurence Pearl Laurence {- dot -} Pearl {- at -} ICR {- dot -} AC {- dot -} UK
Date: 2007-07-10