Hi All,
This will no doubt show something of my ignorance with experimental phasing,
however I'm currently working on solving a 3.8A SAD dataset with Pt anomalous
signal. Both Shelx and Xtriage see reasonable anomalous signal to about 7A and
seem to get statistics suggesting a solution when I
Hi Thomas
We use a very simple solution.
We simply shorten a normal needle to 6.5 mm and push it into another
syringe that has *two *of the white PTFE ferrules made by Hamilton. (We
salvage the extra ferrule from another needle.)
We use a 22 gauge needle (not 22S, where the S stands for *small
If your Pt position is centric then either hand will give a reasonable
looking solution but one will generate LH helices and the other right.
Model building can break that ambiguity - SHELXE and Buccaneer both will
impose correct peptide geometry.
But at such low resolution they may struggle..
What do the twinning tests show? Those space groups can be suspicious, I
believe.
JPK
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of RHYS
GRINTER
Sent: Tuesday, December 16, 2014 4:40 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] P31 or P32
Dear Rhys,
I would try to place idealised secondary structure elements with coot
into the density - at this resolution they probably fit both hands, but
you may see a difference when you do e.g. rigid body refinement.
Best,
Tim
On 12/16/2014 10:39 AM, RHYS GRINTER wrote:
Hi All,
This will
Sorry - of course it can.. Sorry.
Only if the twinning is perfect then you apparently get a higher
symmetry..
Eleanor
On 16 December 2014 at 14:26, Tim Gruene t...@shelx.uni-ac.gwdg.de wrote:
Dear Rhys,
I would try to place idealised secondary structure elements with coot
into the density -
Dear Pietro,
Tim's solution should work for you. If not please let me know.
From CCP4 6.5.0 (due very soon), the default sequence search tool in
MrBUMP will be Phmmer which will be included in the suite on all
supported operating systems. So there won't be the need to download
fasta
Hi Eleanor,
The data is perfectly twinned, with the original auto processing assigning a
point group of P312, but I reprocessed it in P3 and it seems to be behaving
okay.
Are there any additional precautions I should take at the phasing stage with
twinned data?
BW
Rhys
I would say try to get better crystals and data, and also do a MAD experiment.
But...perfect twins are really hard, I think. Maybe vary the crystallization
conditions a bit, additive screen, seeding, etc.
JPK
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK]
But are you sure it is twinned and not really P312?
Ltest etc is a pretty reliable indicator but the results can be biased by
non-crystallographic translation, etc
And do the HA sites obey the twinning symmetry?
On 16 December 2014 at 16:36, Keller, Jacob kell...@janelia.hhmi.org
wrote:
I
I agree here. The 50 % could be a good indicator.
I am finishing a new structure which was about 42% twinned in the monoclinic
setting (b = ~90) for an Se-Met dataset. When I went to refine it with the
native dataset, the twin fraction increased to 50%, figured something wasn't
right.
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Zhiwei Huang’s laboratory at Harbin Institute of Technology (HIT), China.
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