On Thursday 22 October 2009, protein.chemist protein.chemist wrote:
> What is the Sigma Cutoff that one should use for Data Processing using
> HKL2000.
You need to narrow your question. Which "sigma cutoff" are you talking about?
Do you mean the one on the "Index" panel?
It controls the automatic choice of peaks used to determine and refine the
crystal lattice parameters and orientation.
If you have trouble indexing a weak diffraction image, you could try
lowering this cutoff so that more peaks are used for indexing.
Conversely, if your diffraction pattern is complicated by weak Bragg
peaks from a secondary crystal fragment then it might help to set the
cutoff higher in the hope that it would tend to select only the most
intense peaks from the primary lattice.
> Is there a minimum or maximum value.
>
> Also if there is a variation then what all does it depend on.
>
> Thanks in Advance for your help.
>
> Mariah
>
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