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 _____________________________________________________________ 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
