PEG 3350 can also provide some cryoprotection; 22% PEG 3350 with 5%
glycerol has proved a good cryoprotectant in my hands.
kmj
Phoebe Rice wrote:
If you have high [DTT] in your buffer, you might be
catalyzing the addition of dimethyl arsenic (from the
cacodylate) to some of your cysteines?
Also, 10% glyercol sounds quite low for reproducibly good
freezing (at least in my experience).
Phoebe
---- Original message ----
Date: Mon, 2 Jun 2008 17:04:38 +0100
From: sajid akthar <[EMAIL PROTECTED]>
Subject: [ccp4bb] crystallisation
To: CCP4BB@JISCMAIL.AC.UK
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/
________________
DSCN0003.JPG (720k bytes)
Phoebe A. Rice
Assoc. Prof., Dept. of Biochemistry & Molecular Biology
The University of Chicago
phone 773 834 1723
http://bmb.bsd.uchicago.edu/Faculty_and_Research/01_Faculty/01_Faculty_Alphabetically.php?faculty_id=123
RNA is really nifty
DNA is over fifty
We have put them
both in one book
Please do take a
really good look
http://www.rsc.org/shop/books/2008/9780854042722.asp
