[ccp4bb] plate crystal optimization

[Rakesh Chatterjee]

hello everyone,
i have a protein which co-purifies with a ligand (small molecule ~
810 Dalton). i didn't know what kind of ligand is it so i am planing to
identify it. meanwhile my protein crystallized as plates and while
diffracting i found that the crystal is showing a good diffraction pattern
upto 2.6 Angstroms in home source Cu K-alpha. however when the crystal
rotates between 90 degrees to 135 degrees, the spots become streaky. should
i try different cryo-MPD/ PEG400 etc? to circuvent the problem i did some
additive screen but was not of much help. any valuable suggestion willbe
handfull.

thanx in advance
rakesh

Re: [ccp4bb] plate crystal optimization

[Phoebe A. Rice]

Among many possible reasons, the streaking could be caused mechanical stress to 
the thin plates during mounting.  Have you tried those loops that look like 
miniature tennis rackets?

  Phoebe



From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Rakesh 
Chatterjee [rakesh.2665...@gmail.com]
Sent: Monday, April 01, 2013 10:01 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] plate crystal optimization

hello everyone,
i have a protein which co-purifies with a ligand (small molecule ~ 810 Dalton). 
i didn't know what kind of ligand is it so i am planing to identify it. 
meanwhile my protein crystallized as plates and while diffracting i found that 
the crystal is showing a good diffraction pattern upto 2.6 Angstroms in home 
source Cu K-alpha. however when the crystal rotates between 90 degrees to 135 
degrees, the spots become streaky. should i try different cryo-MPD/ PEG400 etc? 
to circuvent the problem i did some additive screen but was not of much help. 
any valuable suggestion willbe handfull.

thanx in advance
rakesh

Re: [ccp4bb] plate crystal optimization

[Raji Edayathumangalam]

I hate to take you back to the step of crystallization but have you tried
seeding to improve the crystal morphology/volume? If tinkering around with
cryoprotectants and mounting techniques does not help your case, seeding
might be worth considering. In some of the cases I've seen, my labmate was
able to transform plates into 3D crystals. Of course, if there's good
reason one is getting plates in the first places, seeding may not help.
Just to keep that in the back of your mind given the magical
transformations I've witnessed.

Good luck!
Raji



On Mon, Apr 1, 2013 at 11:19 AM, Phoebe A. Rice pr...@uchicago.edu wrote:

  Among many possible reasons, the streaking could be caused mechanical
 stress to the thin plates during mounting.  Have you tried those loops that
 look like miniature tennis rackets?

   Phoebe

  --
   *From:* CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Rakesh
 Chatterjee [rakesh.2665...@gmail.com]
 *Sent:* Monday, April 01, 2013 10:01 AM
 *To:* CCP4BB@JISCMAIL.AC.UK
 *Subject:* [ccp4bb] plate crystal optimization

   hello everyone,
 i have a protein which co-purifies with a ligand (small molecule ~
 810 Dalton). i didn't know what kind of ligand is it so i am planing to
 identify it. meanwhile my protein crystallized as plates and while
 diffracting i found that the crystal is showing a good diffraction pattern
 upto 2.6 Angstroms in home source Cu K-alpha. however when the crystal
 rotates between 90 degrees to 135 degrees, the spots become streaky. should
 i try different cryo-MPD/ PEG400 etc? to circuvent the problem i did some
 additive screen but was not of much help. any valuable suggestion willbe
 handfull.

  thanx in advance
 rakesh




-- 
Raji Edayathumangalam
Instructor in Neurology, Harvard Medical School
Research Associate, Brigham and Women's Hospital
Visiting Research Scholar, Brandeis University