The density looks an awful lot like a polyatomic anion (sulfate,
phosphate, etc.). It's hard to tell from the fixed images, but it
appears to be tetrahedral. Is there any chance a polyatomic anion could
be in the crystallization solution? Perhaps from the protein stock solution?
Sampath Natarajan wrote:
Dear All,
Currently I'm modeling one structure with 2.6A data. I could find an
unknown density which I located in the interface between the three
similar subunits. This density shows very strong peak, which appears
until 10 sigma level in the difference map. It seems to be a metal
ion. But, already I could find two Zn ions in the active site and
refined well. The aspartic acid of each subunit has very close
interaction with this density. You can see the pictures, which I have
attached with this mail. The crystallization condition is 0.05M CaCl_2
0.1M Bis-Tris pH 6.5, 30% (/v/v/) PEG monomethyl ether 550. Suggestion
about this unknown density will be more helpful to find the molecule.
thanks a lot,
Regards,
Sampath
--
------------------------------------------------------------------------
Roger S. Rowlett
Professor
Colgate University Presidential Scholar
Department of Chemistry
Colgate University
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Hamilton, NY 13346
tel: (315)-228-7245
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fax: (315)-228-7935
email: rrowl...@mail.colgate.edu
