Hello All,
This is regarding twinning in a data set.
I collected a native data set to resolution, 1.8 A. I used XDS suite
to process and scale the data set. It scaled well in P622 and I found
systematic absence (l=6n present).
Hence thought the space group may be P6122/P6522. SFCHECK did not
show any twinning and also it did not detect pseudo-translation. Twin
test in
http://nihserver.mbi.ucla.edu/pystats/ ( Merohedral Twin
Detector: Padilla-Yeates Algorithm ) showed perfect twinning.
Scaled in P61/65 and SFCHECK reported twinning fraction 0.272 & no
pseudo-translation.
http://nihserver.mbi.ucla.edu/pystats/ ( Merohedral Twin Detector:
Padilla-Yeates Algorithm ) showed perfect twinning.
Another server from ucla
http://nihserver.mbi.ucla.edu/Twinning/showed partial twinning with twin fraction 0.23 as follows.
2 along a, b, a*, b*
No. Twin Law Related Reflections = 18033 (pairs)
No. Twin Law Pairs Considered = 9016
<H> = 0.266149
<H2> = 0.095303
Twin Fraction = 0.233249 +/- 0.000602
(SHELXL Commands: TWIN 1 0 0 -1 -1 0 0 0 -1 and BASF 0.233249)
In P61/65, I got the following matthews-coeffs
mol/asym Matthews Coeff %solvent P(1.73) P(tot)
_____________________________________________________________
1 9.75 87.39 .00 .00
2 4.88 74.79 .00 .01
3 3.25 62.18 .06 .14
4 2.44 49.57 .57 .63
5 1.95 36.97 .36 .21
6 1.63 24.36 .00 .00
7 1.39 11.75 .00 .00
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May I ask what could be the real twin fraction and what is the
likelihood of solving the structure by molecular replacement by models
with 25 % sequence identity and 30 % sequence similarity.
Thank you so much for reading this mail during your busy hours and
all suggestions, comments would be gratefully welcome & appreciated.
thank you ccp4 mailing list.
John