Hi Alex,
Was it purified via a Ni2+ resin? Is the protein oligomeric in
solution? Could it have stripped an ion out during purification and
brought it all the way through to crystallisation?
Have you tried refining a Ni2+ in the location?
JP
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-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of
Alex Singer
Sent: 24 February 2011 00:35
To: [log in to unmask]
Subject: [ccp4bb] strange density
Hi -- I have a high resolution structure (1.6 A) where I'm ready to
deposit except I have some very strange density, shown in the two
pictures here -- sort of a sphere with a split cresent around it,
falling between molecule A and B His 138 imidazole rings. The sphere is
modeled as a Cl atom, more for "kicks" because resulting 2Fo-Fc maps
still have considerable positive difference density throughout the
sphere. There are 4 molecules in the AU, the imidazole ring of H138 in
molecules C and D point into a solvent channel.
Crystallization conditions are 0.2M Mg Chloride, 0.1M Bis-Tris pH6.5,
25% PEG3350, cocrystallized in 2.5mM Glycero-3Phosphocholine and
cryoprotected by dipping in Paratone_N oil.
Let me know what you're thoughts are and thank you for your help.
Alex Singer
--
Dr. Alex Singer
C.H. Best Institute
112 College St. Room 70
University of Toronto
Toronto, Canada, M5G 1L6
416-978-4033
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