Dear James,
your challenge in its current form ignores an important source
of information for model building that is available for your
simulated data - namely, it does not allow to use anomalous
phase information in the model building. In difficult cases on
the edge of success such as this one,
Dear James,
I agree with Pavel that your example is not very realistic. In practice
one would start from the heavy atom positions. As well as providing
starting phases, they are useful in other ways. For example. shelxe
(and probably most other tracing programs) adds them to a 'no-go'
map so it
Fair enough!
I have just now added DANO and I(+)/I(-) to the files. I'll be very
interested to see what you can come up with! For the record, the phases
therein came from running mlphare with default parameters but exactly
the correct heavy-atom constellation (all the sulfur atoms in
Fair enough!
The heavy atom positions are simply the S atoms in 3dko. There are 22
of them. Also, in this case the Met side chains (12 of those) are 32%
occupied with Se. The other 68% is sulfur. I think it is realistic
that one could know the extent of Se incorporation ahead of time
Woops! sorry folks. I made a mistake with the I(+)/I(-) entry. They
had the wrong axis convention relative to 3dko and the F in the same
file. Sorry about that.
The files on the website now should be right.
http://bl831.als.lbl.gov/~jamesh/challenge/possible.mtz
James,
I had in fact just come to the conclusion that the indexing was
consistent with 3dko for 'possible' but not for 'impossible',
which I suppose was logical.
George
Woops! sorry folks. I made a mistake with the I(+)/I(-) entry. They
had the wrong axis convention relative to 3dko and
I admit that made impossible more difficult to solve than possible,
but not in the way I had intended! Again, sorry about that. It is
corrected now.
The change in indexing arises because I am processing the simulated
images with a default run of XDS and as you know the autoindexing picks
I can build from the impossible.mtz data in the following two steps:
1. getting the SE substructure from anomalous difference map
constructed from impossible.mtz
2. running combined model building using the substructure
from step 1 and starting from the impossible.mtz map
Only impossible.mtz
