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CCP4BB  June 2008

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Subject:

Re: crystallisation and mosaicity

From:

"Ohren, Jeffrey" <[log in to unmask]>

Reply-To:

Ohren, Jeffrey

Date:

Wed, 4 Jun 2008 09:37:02 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (82 lines)

Could it be that evaporation on the way from the microscope to the cold
stream increases the effective cryo concentration as well as causing a
beneficial dehydration effect? 

There are quite a few publications that have carefully evaluated
optimizing cryo cooling. Check out Elspeth Garman's many excellent
papers on the subject as well as J. Appl. Cryst. (2006). 39, 244-251;
Methods 34 (2004) 415-423 and Acta Cryst. (2002). D58, 459-471, to name
a few. 

Jeff

-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of
Paul Paukstelis
Sent: Tuesday, June 03, 2008 11:59 PM
To: [log in to unmask]
Subject: Re: [ccp4bb] crystallisation and mosaicity

I have also observed this. In my cases I have also been able to get away

with using less cryoprotectant when freezing in the cryostream.

--paul

Daniel Pomeranz Krummel wrote:
> Dear Sajid,
>
> I have observed a consistent reduction in mosaicity (from approx. 0.95
to
> 0.45) for one case by freezing the crystals in a cryostream (N2
vapour) as
> opposed to submerging in liquid nitrogen.
>
> Have others observed this?
>
> Daniel
>   
>> Dear All
>>
>> My protein size is ~30kD and crystallizes with
>> 19%Peg3350, 0.2M Nacl, and 0.1M Na Cacodylate buffer.
>>
>> Please refer the attached crystal image with this. The
>> crystal looks like good enough for home source. These
>> crystals appears in 4-5 days at room temp.
>>
>> Sometimes I'm getting crystals like this, but very few
>> in 24 well tray. Most of the time, I found the drop
>> contains needles. If I reduce the precipitant little
>> bit, I wont find any change in the drop even after
>> long time. Changing pH (or temp)of the buffer does not
>> help me any better. The crystal appears only around
>> 5.5pH.
>>
>> The problem is mosaicity. This crystal diffracted in
>> home source upto 3.2A and the mosaicity is 2.5degree.
>> Almost all the good crystal like this having same
>> mosaicity.
>>
>> Good cryo condition so far that I found was
>> 10%Glycerol with mother liquor. Other conditions
>> weekens the diffraction quality or increase mosaicity.
>>
>> In many crystal I could see some crack in the middle
>> of the crystal, it looks like twin crystal. Or the
>> crystal appears with some sattelite crystals.
>>
>> Can anyone suggest me some good way to overcome these
>> problems.
>>
>> Thankz
>>
>> Sajid
>>
>>
>>
>>       From Chandigarh to Chennai - find friends all over India. Go to
>> http://in.promos.yahoo.com/groups/citygroups/
>>     
>
>   

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