Remember that since it is on a special position (2-fold?), you may not
be looking at a single object, but an overlay from two or more
positions.
The anomalous map is very useful; the mystery molecule must have an
anomalous scatterer. It would be even more helpful if you had mentioned
the wavelength of the data. Anyway, the only thing in the list of mother
liquor ingredients you provided that scatters anomalously is calcium,
which fits in with the Asp ligands. The additional ligands for the
calcium might be water or acetate.
So: my guess would be two positions of Ca2+, one right on the axis and
one off the axis (and doubled by the symmetry). You can try placing Ca
atoms at these positions and see what the occupancies and thermal
factors refine to. For example, start with an occupancy of 0.5 at each
position and see if the thermal factors refine to a value comparable to
nearby protein atoms.
Cheers,
-
=======================================================================
With the single exception of Cornell, there is not a college in the
United States where truth has ever been a welcome guest - R.G. Ingersoll
=======================================================================
David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[EMAIL PROTECTED]
On Mon, 2008-02-25 at 11:54 +0100, Franck Coste wrote:
> As Edward MITCHELL suggested, I made a phased anomalous difference map
> and could clearly see the S atom of my sulfide bridges and 1 Ca atom as
> I espected. Concerning the unknown density, the shape is the same as in
> the fo-fc map ???? Updated images at :
> http://unknowndensity.blog4ever.com/blog/photo-183078.html
> In yellow is the phased anomalous difference map at 4 sigma.
> Franck.
