RE: [ccp4bb]: large cell

[Kostrewa Dirk <dirk.kostrewa@psi.ch>]

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Dear Stefan,

often, crystals showing large unit cell axes ratios have a clear shape and
it is (even with loops) quite often possible to mount them such that you
rotate around the long axis. By this, you avoid the travelling of
reflections close in reciprocal space perpendicular through the Ewald
sphere. By the way, in your formula you've forgotten to multiply by 180/Pi
which would give a delta-phi of -0.24 assuming a mosaicity of 0.6 degrees.
Anyway, by rotating around the long axis, you could measure up to ~0.86
degrees per frame (because with gamma=120 deg, the spacing in reciprocal
space of your 136 A axis is equivalent to 136*sin(120)=117.8 A).

Good luck,

Dirk.

*****************************************************
Dirk Kostrewa
Paul Scherrer Institut   e-mail: dirk.kostrewa@psi.ch
Life Sciences             phone: +41-56-310-4722
OSRA/007                    fax: +41-56-310-4556
CH-5232 Villigen PSI        WWW: http://sb.web.psi.ch
Switzerland
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> -----Original Message-----
> From: Stefan Henrich [mailto:henrich@biochem.mpg.de]
> Sent: Dienstag, 25. Juni 2002 11:45
> To: CCP4
> Subject: [ccp4bb]: large cell
> 
> 
> ***  For details on how to be removed from this list visit the  ***
> ***          CCP4 home page http://www.ccp4.ac.uk         ***
> 
> Dear all,
> I have crystals in spacegroup P3 (maybe higher symm) with 
> cell constants
> of about 136 A, 136 A, 475 A,  90.00  90.00 120.00 and unfortunately a
> mosaicity of about 0.6.
> I know that I need theoretically: deg(delta phi + mosaic) <= dmin (3.0
> A) / longest axis (475 A). This would mean (delta phi + 
> mosaic) have to
> be less than 0.36 degrees instead of 0.7 (delta phi 0.1 + mosaic 0.6).
> Is there a strategy to overwhelm this problem?
> Thanks
> 
> Stefan
> 
> --
> Stefan Henrich
> home:                    work:
> Wuermtalstr. 142       Max-Planck-Institut fuer Biochemie
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>                          +49 89/ 8578 -2685 (lab K305)
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> 
>