You must be carefulwith assigning twinning operators in a lower symmetry
than the true one. Some twinning tests look for correlations between
reflections which would be related by the twinning operator.
eg a twinning operator for PG 4 is k,h,-l so the CC between h,k,l, and
k,h,-l is checked.
B
Hi -
I would agree with the twining possibility - I4122 is guilty until
proven innocent ;-)
As for the SHARP idea, I don't think that SAD phasing again would
help. At 3.2 A resolution,
and if radiation damage permits, good old MAD (phased by SHARP
naturally ...) will most likely give you
Hi, Joe,
1,Try SHARP and then check the quality of the map. If good, continue,
if bad, need re-examine your data. I Think SHARP is good for your case.
2, Do not give up the possibility of twinning. A lower symmetry plus a
nearly perfect twin operator might mislead to a higher symmetry.
Yanmin
I'd try to
1) make sure your data reduction is optimal - try at least one other program,
and not only your favourite one!
2) as this is SAD: use SHARP to get the best experimental phases, plus density
modification for a map without model bias
3) incorporate the experimental phase information int
Mark,
The bulk solvent model in CNS 1.2 is now perfectly stable at low
resolution. No need
to fix the solvent parameters anymore.
Axel
Mark A. White wrote:
Joe,
1) The bulk solvent models in CNS and REFMAC are not stable at low
resolution. Fixing the bulk solvent B-factor can improve th
Merge in the lower symmetry space group you mentioned and refine with a
twinning operator.
xtriage can tell you what the twinning operator is and phenix.refine can
do the twinned refinement.
In my experience, these kinds of stats almost always indicate an
incorrect symmetry choice somewhere
Joe,
1) The bulk solvent models in CNS and REFMAC are not stable at low
resolution. Fixing the bulk solvent B-factor can improve this behavior.
2) With low resolution data model-bias becomes a serious issue when
working with a MR solution. I have found that DM (with or withou NCS)
can improve l
These problems are horrible!
1) I usually try to run refinement using the exptl phases as restraints.
It is worth getting the best possible phases before you start - DM with
66% solvent should make a great improvement..
Then these cam be used as restraints for the refinement, and your FWT
m
Hi Joe,
have you tried to process the data in different programs ? This can
sometimes make a dramatic difference, being completely unbiased I would
recommend XDS over Mosflm or HKL2000. Was your data carefully collected
? How many rejections, overlaps do you have ?
Juergen
--
Jürgen Bosch
U
Hi all,
We have data sets for a protein-RNA complex at 3.2 A resolution. . The
data belong to the space group I4122 and contains one molecule of
Protein-RNA complex (300AA and 16nt; 66% solvent content) in the asym
unit. We have managed to get phases using Se-SAD and the present model
contains 60%
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