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
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