Re: [ccp4bb] Help with reducing crystal mosaicity

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

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Subject: Help with reducing crystal mosaicity
From: Mary Fitzgerald mary {- dot -} x {- dot -} fitzgerald {- at -} GMAIL {- dot -} COM
Date: 2007-07-09

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Subject: Re: Help with reducing crystal mosaicity
From: "David J {- dot -} Schuller" djs63 {- at -} CORNELL {- dot -} EDU
Date: 2007-07-09

Subject: Re: Help with reducing crystal mosaicity
From: Jim Pflugrath Jim {- dot -} Pflugrath {- at -} RIGAKU {- dot -} COM
Date: 2007-07-09

What is the mosaicity of the unfrozen crystal?

Jim

-----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

CCP4bb navigation

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

Previous message:
Subject: Help with reducing crystal mosaicity
From: Mary Fitzgerald mary {- dot -} x {- dot -} fitzgerald {- at -} GMAIL {- dot -} COM
Date: 2007-07-09

Next message:
Subject: Re: Help with reducing crystal mosaicity
From: "David J {- dot -} Schuller" djs63 {- at -} CORNELL {- dot -} EDU
Date: 2007-07-09