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A bit late but I didnt answer in time. This is one of the cases where I still wheel out ALMN to do the self rotation. It generates ALL symmetry peaks and allows you to select which axis you want to take as the polar axis. (ncode = 1 c*, ncode = 2 a*, ncode = 3 b* and so on) And the program output also makes an attempt to explain what it is doing! A script #!/bin/csh -f # almn \ hklin /y/people/ccp4/projects/mao/maon5_all_scaleit1.mtz \ MAPOUT /y/work/ccp4//almn.map \ <<eof SELF 3 25 RESO 10 3.5 TITL Jean CRYS file 1 orth 1 flim 1 10000000000000 LABI FILE 1 F=F_natlo LIMIT 0 180 5 1 ! Beta limit 90 because of symmetry ! If in doubt set Beta limit 180.. FIND 5 40 NOPR MAP END eof Dirk Kostrewa wrote: > Dear CCP4ers, > > I've asked you about symmetry in stereographic projections of > self-rotation functions, because I have in a monoclinic space group > with beta=97 a peak for a NCS 7-fold axis at Phi=83, Psi=90, > Kappa=51.4. In this self-rotation function, calculated with GLRF, the > monoclinic b-axis is oriented from south-pole to north-pole. Thus, > with Psi=90, the 7-fold lies in the a,c-plane, and I was wondering > wether it points along the c-axis by some symmetry element, since > 83=180-97. Pierre Rizkallah pointed to the fact that the self-rotation > function is calculated in Patterson space which has an inversion > centre, and Ian Tickle has pointed me to the POLARRFN documentation > that discusses some of these symmetries. From this, I can, in my case, > construct the following symmetry-equivalent positions: > > (1) Original Peak: Phi, Psi, Kappa ---> > 83, 90, 51.4 > (2) General equivalent position: 180+Phi, 180-Psi, -Kappa ---> > 263, 90, -51.4 > (3) Crystallographic Dyad || Poles: 180+Phi, Psi, Kappa ---> > 263, 90, 51.4 > (4) (3) combined with (2): Phi, 180-Psi, -Kappa ---> > 83, 90, -51.4 > > Thus, none of these combinations gives a Phi-angle of 97 degrees. > However, meanwhile Liang Tong, the author of GLRF, explained to me, > that in his convention, a positive Phi angle goes from +X (=a) to -Z > (=-c*), which means that Phi=83 points really along the (-)c-axis > (thus confirming my initial hypothesis). > > 7-fold > / > / > / > b-------------- a > /| > / | > / | > / | > c c* > > So, many thanks to all of you who replied and helped me to solve this > puzzle! > I would still be interested in a textbook or paper discussing symmetry > in stereographic projections, though ... > > Best regards, > > Dirk. > > Am 22.11.2007 um 14:40 schrieb Dirk Kostrewa: > >> Dear CCP4ers, >> >> does any of you have a good reference describing the symmetry of >> crystallographic stereographic projections? There is a lot of >> literature describing rotational symmetry in Eulerian angular space, >> but I'm not aware of any for polar angles. In particular, I've >> calculated a self-rotation function for a crystal in space group C2 >> with a monoclinic beta-angle of 97 degrees in a convention where Phi >> is the angle from the x-axis (=a-axis) and Psi is the angle from the >> monoclinic b-axis. I get a beautiful peak for a seven-fold rotation >> axis at Phi=83 degrees and Psi=90 degrees. I think that the >> seven-fold NCS-axis should point along the crystallographic c-axis, >> but then I would expect Phi=97 and Psi=90. Presumably, there must be >> a symmetry with the term Phi' = 180-Phi, but I would like to _know_ >> it. I would be grateful for any pointer to a good reference >> describing symmetry in crystallographic stereographic projections, >> also for future cases. >> >> Best regards, >> >> Dirk. >> >> ******************************************************* >> Dirk Kostrewa >> Gene Center, A 5.07 >> Ludwig-Maximilians-University >> Feodor-Lynen-Str. 25 >> 81377 Munich >> Germany >> Phone: +49-89-2180-76845 >> Fax: +49-89-2180-76999 >> E-mail: [log in to unmask] >> ******************************************************* >> >> > > > ******************************************************* > Dirk Kostrewa > Gene Center, A 5.07 > Ludwig-Maximilians-University > Feodor-Lynen-Str. 25 > 81377 Munich > Germany > Phone: +49-89-2180-76845 > Fax: +49-89-2180-76999 > E-mail: [log in to unmask] > ******************************************************* > > >