Hmm - this is odd. For twinning to occur you need two (or more) lattices to overlap..
Your cell is 40.29 66.01 161.37 90.00 94.09 90.00 with symmetry P2/m If I reindex with operator h,k,-h-l the cell becomes: 40.3000 66.0000 163.5358 90.0000 100.1290 90.0000 ie there is not much change in the c length but quite a big change in angle. I think you probably need to process this data as P1 ? Eleanor On 21 October 2016 at 12:04, Robert Gustafsson <[email protected]> wrote: > Hi, > > Space group is P21, cell parameters is 40.29 66.01 161.37 90.00 94.09 90.00 > > From Aimless: > ------------------------------------------------------------ > ------------------------------------ > > | operator | L-test | |Rtwin| | H-test | > Britton | ML Britton | > > ------------------------------------------------------------------------------------------------- > > | -h, -k, h+l | Yes | 0.34 | 0.14 | > 0.11 | 0.05 ( N/A ) | > > ------------------------------------------------------------------------------------------------- > > > > From refmac: > Twin operator: H, K, L : Fraction = 0.806; Equivalent operators: -H, K, -L > > Twin operator: H, -K, -H-L: Fraction = 0.194; Equivalent operators: -H, -K, > H+L > > > In viewhkl summary all columns go to 2.0 Å. > > Robert > > _______________ > Robert Gustafsson > PhD Student > Department of Biochemistry and Biophysics > Stockholm University > 106 91 Stockholm, Sweden > > e-mail: [email protected] > > > > On 21 Oct 2016, at 11:54, Eleanor Dodson <[email protected]> > wrote: > > Hmm - what is your space group, cell, and twin law? > The mtz file output from REFMAC contains detwinned data - ie the column > labelled as F is NOT the measured amplitude derived from the measured > twinned intensities. > > So in some SGs it is conceivable that an index has been generated.. > This shouldnt happen with merohedral twinning but it can with > pseudo-merohedral twinning. > > No the other hand, are you sure the extended resolution does not just > involve the Free R column? look at the viewhkl summary to see if all > columns extend to 2.0 resolution > Eleanor > > > > On 21 October 2016 at 09:24, Robert Gustafsson < > [email protected]> wrote: > >> Hi all, >> >> I am currently refining a structure that is at a resolution of 2.1Å and >> slightly twinned. Below is the message in the aimless results: >> >> WARNING: the L-test suggests that the data may be twinned, so the >> indicated Laue symmetry may be too high >> Rough estimated twin fraction alpha from cumulative N(|L|) plot 0.209 >> +/-(0.015) >> Rough estimated twin fraction alpha from < |L| > 0.202 >> Rough estimated twin fraction alpha from < L^2 > 0.192 >> >> I have been refining with twin refinement, and without, and using twin >> refinement gives better R-factors, as expected. >> >> When looking in the results files more carefully however, it seems that >> 0.1Å of data have been added to my data in the detwinning process! It >> suddenly comes out of refmac with a 2.0 Å in both pdb and mtz resolution, >> and it just suddenly seems to decide that for itself. I have looked for >> differences in my input and there is none other than choosing amplitude or >> intensity based twin refinement, instead of no twin refinement. Input mtz >> and pdb are the same, but in the log file of refmac it suddenly uses 2.0 Å. >> >> This error is not captured afterwards, both Molprobity and PDBe >> validation tool finds the structure to now be 2.0Å resolution, however i >> can see in both refmac output and PDBe validation output that the >> completeness is lowered (which I guess would be expected since some data >> does not exist…) >> >> So the question is, is this a bug of some sort, or should I have chosen >> something in the input of refmac? I am using the latest update of ccp4 >> (7.0.021) using the CCP4i interface. I have looked back at my files ( the >> project started 2 years ago) and the problem was there as well, so it is >> not a new problem. >> >> Sincerely, >> Robert Gustafsson >> >> >> _______________ >> Robert Gustafsson >> PhD Student >> Department of Biochemistry and Biophysics >> Stockholm University >> 106 91 Stockholm, Sweden >> >> e-mail: [email protected] >> >> >> >> > >
