Hi Ian,
many thanks! Apparently, I have to discard now my favorite hypothesis
about the position of the 7-fold ...
Still, if you know about a good reference, I would really like to
read it.
Best regards,
Dirk.
Am 22.11.2007 um 15:28 schrieb Ian Tickle:
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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 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.
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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
E-mail: [EMAIL PROTECTED]
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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 [EMAIL PROTECTED]
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: [EMAIL PROTECTED]
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