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Hi Ian, thanks for the POLARRFN pointer - I've read this before, but I didn't find it complete enough ... Shouldn't the c*-axis have Phi=90, since it is c*=axb? I don't see a peak at 180-Phi, but I thought that there might be other symmetry- equivalent peaks that have some rule for Phi, Psi, Kappa that includes a "Phi-180" term ... but this is why I'm looking for a good reference ... Best regards, Dirk. Am 22.11.2007 um 15:10 schrieb Ian Tickle: > Hi Dirk > > There's a useable (though slightly incomplete) description of the > symmetry of SRF's in the POLARRFN doc, though this only talks about > the > symmetry of the stereographic projection itself and then only about > the > effect of crystallographic dyads. Higher order rotations about z will > obviously produce the same symmetry in the SRF. However higher order > rotations about other axes (e.g. 3-folds in cubic) will not generate > symmetry in the SRF, the peaks will be there of course but in general > positions in spherical polar co-ords. > > In the case you describe, if there were the symmetry phi'=180-phi > wouldn't you expect to see both peaks? > The only crystallographic symmetry in monoclinic with z||b is > phi'=180+phi, so in your case it would appear that your 7-fold NCS > axis > is parallel to c* not c. > > -- Ian > >> -----Original Message----- >> From: [log in to unmask] >> [mailto:[log in to unmask]] On Behalf Of Dirk Kostrewa >> Sent: 22 November 2007 13:41 >> To: CCP4BB >> Subject: Symmetry of crystallographic stereographic projections? >> >> 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] >> ******************************************************* >> >> >> > > > Disclaimer > This communication is confidential and may contain privileged > information intended solely for the named addressee(s). It may not > be used or disclosed except for the purpose for which it has been > sent. If you are not the intended recipient you must not review, > use, disclose, copy, distribute or take any action in reliance upon > it. If you have received this communication in error, please notify > Astex Therapeutics Ltd by emailing [log in to unmask] > and destroy all copies of the message and any attached documents. > Astex Therapeutics Ltd monitors, controls and protects all its > messaging traffic in compliance with its corporate email policy. > The Company accepts no liability or responsibility for any onward > transmission or use of emails and attachments having left the Astex > Therapeutics domain. Unless expressly stated, opinions in this > message are those of the individual sender and not of Astex > Therapeutics Ltd. The recipient should check this email and any > attachments for the presence of computer viruses. Astex > Therapeutics Ltd accepts no liability for damage caused by any > virus transmitted by this email. E-mail is susceptible to data > corruption, interception, unauthorized amendment, and tampering, > Astex Therapeutics Ltd only send and receive e-mails on the basis > that the Company is not liable for any such alteration or any > consequences thereof. > Astex Therapeutics Ltd., Registered in England at 436 Cambridge > Science Park, Cambridge CB4 0QA under number 3751674 ******************************************************* 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] *******************************************************