Re: [ccp4bb]: Problems with SCALA

[Bart Hazes <bhazes@ualberta.ca>]

***  For details on how to be removed from this list visit the  ***
***          CCP4 home page http://www.ccp4.ac.uk         ***

On Mon, 4 Mar 2002, Thomas BERTRAND wrote:

> ***  For details on how to be removed from this list visit the  ***
> ***          CCP4 home page http://www.ccp4.ac.uk         ***
>
> Hi all,
>
> 	I have recently collected data from crystals containing 90 Se-Met in ASU
> from a protein forming an hexamer in Space Group P21. Data were collected
> at ESRF with a CCD ADSC Q210 detector at 2.5A resolution.
> Spots looked very good and a complete data set was collected at the SE-Peak
> Wavelength.
> I used MOSFLM for indexing and everything looked pretty good.
> But when i started SCALA everyting went WRONG !
>
> I don't understand....

One possibility is that you got the beam centre wrong. If the error in the
initial estimate of the beam centre position is large relative to the spacing
between spots, you can get mis-indexed reflections even though the fit looks
good. E.g. if it mis-indexed by 1 along l then the real reflection h,k,l will
be indexed h,k,l+1. Integration and other integration parameters will still be
ok but of course during scaling and merging you will not be comparing symmetry
related reflections leading to horrible statistics. This will also cause SCALA
to blow up the sigma values.

Bart

===============================================================================

Dept. of Medical Microbiology & Immunology
University of Alberta
1-15 Medical Sciences Building
Edmonton, Alberta, T6G 2H7, Canada
phone:	1-780-492-0042
fax:	1-780-492-7521

===============================================================================