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Re: [ccp4bb] cryo-protection for crystals grown in ethanol
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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999
Previous message:
Subject: Re: CCP4i can NOT run
From: Yingjie Peng yingjiepeng {- at -} GMAIL {- dot -} COM
Date: 2008-09-30		Next message:
Subject: precipitates
From: amit sharma 3112amit {- at -} GMAIL {- dot -} COM
Date: 2008-09-30


Subject: Re: cryo-protection for crystals grown in ethanol
From: "Mark J {- dot -} van Raaij" mark {- dot -} vanraaij {- at -} USC {- dot -} ES
Date: 2008-09-30

Dear Rongjin,

I would:
-prepare different cryosolutions, adding glycerol, replacing water
with glycerol, replacing ethanol with other more cryogenic alcohols:
if you have enough crystals, see how these behave when transferred to
these solutions, if they crack, decrease precipitant, if they
dissolve, increase.
once you have measurement time:
-first measure a couple of crystals in a capillary or mitegen "loop
and sleeve" at room temperature to get a "best case" diffraction. On a
home source you might even get a dataset, but surely you'll get good
estimates of mosaic spread, spacegroup, and other crystallographic
parameters, like for instance an idea about if the crystals may be
twinned.
-then measure a couple of crystals directly frozen from the drop (i.e.
"worst-case" scenario).
-then go for complete cryoprotected datasets, using the combined
knowledge of previous experiments.
Even if the upcoming "beamtime" is not enough for all of this and you
have to book more time in the coming weeks, I would go through all
these steps and resist the temptation to go for "quick and dirty". If
you only ever measure at 100K you never know how good the crystals
were before freezing.

Mark

Quoting Rongjin Guan

> Dear All
>
> I got crystals from 20% Ethanol with 0.1M Tris pH 8.5. This is my first
> time to have crystals in Ethanol and want to get some suggestions of
> cryo-protection from those who have done this before.
>
> I am waiting for my time on home X-ray facility, and hope I can get
> some suggestions before that.
>
> Thanks,
>
> Rongjin Guan
>
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