On 10/17/10 15:29, Wu, Mousheng wrote:
Dear All,
I have a MAD dataset at 4Å and shelxD can find clear-cut 10 solutions (my
protein has 12 methionines). I ran autosharp to refine them followed by density
modification. After density modification, I ran solvent flattening. Then I
calculated the anomalous map using the phase from sharp and the electron
density map from solvent flattening. The anomalous map shows the density
around these 10 selenium sites are clear and round. However, the density map
from solvent flattening showed that only 4 selenium sites have clear and round
density. The density around these 4 sites clearly showed beautiful helices.
surprisingly, other 6 selenium sites have poor density or no density at all.
The electron density around them is not very good and the predicted helical
density is flat. I check the electron density before I ran solvent flattening.
The result is same. I am quite confused about the big difference from these
two maps. I also try SnB to find the selenium sites. The solutions are same as
those from ShelxD. But How to explain the poor density around the selenium
sites in the density modification map? Is there any problem with my selenium
sites? Any suggestion from crystallographic experts? Thanks.
Solvent flattening is one form of density modification, so your
description of what you did is a bit confusing. Did you use the
appropriate solvent content for the solvent flattening?
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All Things Serve the Beam
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David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[email protected]
