Re: [ccp4bb] Help with reducing crystal mosaicity

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

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Subject: BEAMTIME at BM14 at the ESRF -proposal deadline
From: "Martin A {- dot -} Walsh" walsh {- at -} ESRF {- dot -} FR
Date: 2007-07-11

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Subject: Re: Help with reducing crystal mosaicity
From: "Benini, Stefano" Stefano {- dot -} Benini {- at -} ASTRAZENECA {- dot -} COM
Date: 2007-07-11

Subject: Re: Help with reducing crystal mosaicity
From: Patrick Shaw Stewart Patrick {- at -} DOUGLAS {- dot -} CO {- dot -} UK
Date: 2007-07-11

Just a thought, Mary - going back to your original question about MPD. I extracted the crystallization conditions from REMARK 280 of 3939 PDB entries a couple of years ago. The average concentration of the MPD used was high - 38.6%, while PEGs tended to be used at lower concs, e.g. PEG400 25.7%. You can see the data at www.douglas.co.uk/top14.htm

I thought this information could be useful if you want to replace some of the MPD with another precipitant (or cryoprotectant).

Best wishes

Patrick Shaw Stewart

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> -----Original Message-----
> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Mary
> Fitzgerald
> Sent: 09 July 2007 23:05
> 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

CCP4bb navigation

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

Previous message:
Subject: BEAMTIME at BM14 at the ESRF -proposal deadline
From: "Martin A {- dot -} Walsh" walsh {- at -} ESRF {- dot -} FR
Date: 2007-07-11

Next message:
Subject: Re: Help with reducing crystal mosaicity
From: "Benini, Stefano" Stefano {- dot -} Benini {- at -} ASTRAZENECA {- dot -} COM
Date: 2007-07-11