[ccp4bb] Your opinion about the attached diffraction pattern

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

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From: Lijun Liu liulj {- at -} UOXRAY {- dot -} UOREGON {- dot -} EDU
Date: 2008-04-03

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Date: 2008-04-03

Subject: Your opinion about the attached diffraction pattern
From: Ibrahim Moustafa I {- dot -} moustafa {- at -} PSU {- dot -} EDU
Date: 2008-04-03

Dear CCP4 users,

I¹m trying to crystallize a a small protein, 200 aa. Screening showed one
promising hits which was further optimized by additive screen.
Finally a beautiful crystal was obtained from conditions: 30% PEG4000 + 0.2
M Ammonium sulfate + 10 mM LaCl3. I was optimistic that the crystal
Is a protein not a salt as the salt conc. is low in the crystallization
buffer and LaSO4 would be soluble if it is formed. However, testing the
Crystal on the local source showed a weird diffraction pattern, see the
attached picture. It is clear that the crystal has a salt, from the strong
Spots in the diffraction, also depending on the rotation angle, some images
showed a clear salt. On the other hand there are closer spots
Suggesting the presence of proteins (may be fibrous). Washing few crystals
and running a gel revealed the presence of the protein.

My question is what could be the diffracting object that gave the attached
pattern? Could it be a salt crystal with a non-ordered protein inside?!
If it is the case, has any body went through the same experience and got
success to optimize the condition to get real protein crystal?
I¹d be appreciated if people want to share their experience and to see what
do they think of the pattern in the attached pic.

Thanks in advance for your shared thought.

Best,
Ibrahim
--

Ibrahim M. Moustafa, Ph.D.
Biochemistry and Molecular Biology Dept.
201 Althouse Lab., University Park,
Pennsylvania State University
PA 16802

Tel. (814) 863-8703
Fax (814) 865-7927

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: twinned?
From: Lijun Liu liulj {- at -} UOXRAY {- dot -} UOREGON {- dot -} EDU
Date: 2008-04-03

Next message:
Subject: Re: Off topic: PDI overexpression in HEK293 cells
From: Kenneth Verstraete kenneth {- dot -} verstraete {- at -} UGENT {- dot -} BE
Date: 2008-04-03