Hi Sajid,
congratulations to your nice looking crystals. I'm not sure if someone
already sugested to mount smaller crystals ?
You write they need 4-5 days, I assume you can already see them earlier
before they reach that size. Am I roughly right in the assumption that
these crystals are about 50-70 x 50-70 x 800 micrometers ?
At what part of the crystal do you shoot after having mounted it ?
Are you using a loop which would fit the crystal or a smaller loop ?
If using a smaller loop try shooting at parts of the crystal which are
within the loop and check the part that sticks out of the loop. Try to
reduce the beamsize to the size of the crystal.
Since you know that glycerol is good, try adding other cryo-protectants
in combination e.g. MPD, EG or small PEGs
Good luck,
Juergen
sajid akthar wrote:
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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Jürgen Bosch
University of Washington
Dept. of Biochemistry, K-426
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