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
