Re: [Fwd) ccp4 problem stuff

["Eleanor J. Dodson" <ccp4@ysbl.york.ac.uk>]

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Scott White wrote:
> 
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> 
> Dear all,
> 
> I am experiencing some problems with the refinement (fiting) step of
> AMORE. My crystal appears to be P21 (a=71.23 b=57.26 c= 116.79,
> alpha= 90 beta = 103.27 gamma= 90) with b-axis unique. The data were
> integrated and processed in mosflm and scaled in scala (R < 5%). 0k0
> reflections clearly indicate a 2-fold screw axis. AMORE appears to
> work fine giving translation search results of
> 
> alpha = -0.05  beta = 88.66  gamma = 345.08
> Tx = 0.2019 Ty = 0.000 Tz = 0.4464
> Cc = 24.3 Rfac = 56.3
> 
> Upon refinement (the fiting step) the value for a fractional
> translation in Ty increases enormously often giving a line of
> asterisks e.g. (for above example)
> 
> alpha = -1.46 beta = 87.93 gamma = 344.55
> Tx = 0.2038 Ty = ***** Tz = 0.4493
> Cc = 43.3 Rfac = 54.0
> 
> This crystal is of a protein which can also grow in a tetragonal form
> where the c axis is large (over 250 Angstroms)
> 
> Could anyone offer any advice on where possible reasons for this come
> from and how best to tackle them, thanks
> A.Lovering
> University of Birmingham, U.K.
> 
> a.l.lovering@bham.ac.uk


 Since this is a polar space group the Y coordinate cannot be
determined.

 You should not try to fit Y at all, and in the new release the program
will in fact turn that fitting parameter off. In fact the solution is
perfectly valid - you CAN set y to 1234567654.789 if you fancy.. but it
is not helpful!
 Set iy back to 0.00 for convenience..

 Eleanor Dodson

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Eleanor J.Dodson, Chemistry Department, University of York, U.K.
Tel: Home +44 (1904) 42 44 49, work:  +44 (1904) 43 25 65
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