Hi Dirk
Sorry yes you're right I'm talking nonsense, c* will be at phi=90;
that's what comes of not making a diagram! As far as the description of
dyads goes the POLARRFN description is complete. It's only incomplete
for higher order axes, so I think the symmetry you hope to find doesn't
exist.
Cheers
-- Ian
> -----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]] On Behalf Of Dirk Kostrewa
> Sent: 22 November 2007 14:21
> To: CCP4BB
> Subject: Re: [ccp4bb] Symmetry of crystallographic
> stereographic projections?
>
> 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
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> *******************************************************
> 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
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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.
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