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[ccp4bb]: MOSFLM warnings - problem solved
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Firstly, I would like to acknowledge the kind help I received from you all who suggested
possible solutions for the problem.
Although it may be difficult to point to the exact cause of the problem, it was identified
and solved.
Bellow is a summary.
If you have more comments or advices, they are very welcomed.
Thank you very much,
Ricardo Aparicio
IFSC/USP - Brazil
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What was happening...
====================
After playing with resolution limits, integration in P1, comparison between fulls and
partials, loggraphs against resolution and batch (all statistics), changes in the
mosaicity values, I finally could solve the problem.
All of the previous tests were OK, no significant differences between Rmerges of fulls and
partials, no problems at all when looking at Rmerge vs. batch and so on.
The answer came from Dr. Leslie's e-mail:
> You should be able to locate the image(s) where the missets
> change by 0.13 degrees. If you can't find it, then there is no need to
> worry.
> One situation which can give rise to apparent large changes in the
> crystal orientation is if the diffraction is very weak, so there are
> only strong spots near the centre of the image. In these
> circumstances, the orientation of the crystal around the X-ray beam
> direction (PSIX) which is derived from the spot positions, is poorly
> determined. Normally this is also associated with large variations in
> the TILT and TWIST parameters (eg shifts of more than 10 between
> adjacent images) and ROFF and TOFF for radial readout image plate
> scanners.
I have identified this problem in the first 20 images with an acute change in TILT and
Misset angles starting from img10.
Visually they are "perfect" and and I/sigma(I) is as good as the other images.
Integration starting from the images where Misset angles start to stabilize works perfectly.
I also note that now I have 0.024 Rmerge against the previous 0.035 in the lowest
resolution shell (in addition to lower values in all the resolution range).
> If the images are not weak and you really have shifts in orientation,
> you should double check that your goniometer heads do not have any
> play and that the magneting coupling for your cryo-pins are clean and
> strong.
Maybe a misplaced cryo-pin...
Fortunately, because data collection is under way, it is still time to have a look.
For curiosity, here is the Misset Table from loggraph:
Image PHIX PHIY PHIZ
2.00 0.10 -0.19 0.18
3.00 0.11 -0.19 0.16
4.00 0.10 -0.19 0.18
5.00 0.11 -0.19 0.16
6.00 0.10 -0.19 0.17
7.00 0.11 -0.19 0.15
8.00 0.09 -0.20 0.16
9.00 0.07 -0.22 0.16
10.00 0.02 -0.23 0.13 * suddenly changes
11.00 -0.05 -0.16 0.05 *
12.00 0.00 -0.03 0.02
13.00 0.06 0.06 -0.06
14.00 0.12 0.16 -0.08
15.00 0.15 0.23 -0.10
16.00 0.17 0.27 -0.10
17.00 0.19 0.31 -0.12
18.00 0.22 0.34 -0.10
19.00 0.23 0.34 -0.10
20.00 0.25 0.34 -0.09 -> starts to stabilize...
21.00 0.25 0.36 -0.10
22.00 0.26 0.37 -0.09
23.00 0.26 0.36 -0.10
24.00 0.26 0.36 -0.10
25.00 0.26 0.36 -0.12
26.00 0.25 0.36 -0.12
27.00 0.25 0.36 -0.13
.....