processing data with ice ring

From: Shanti Pal Gangwar
Date: 30 March 2012 05:30

  Hello all,

I have a query regrading processing of data.  I have  good diffraction data that  has ice rings. Is it possible to mask the regions of the ice rings during processing?
I have been using Mosflm to process data.  
Is this feature available with this program? 

Suggestions and advice would be greatly appreciated.

Thanks


regards

SHANTI PAL






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From: Sita Ram Meena
Hi Shanti

Mosflm has a default option in the "processing options" menu.

when you runs imosflm  go to the setting and than processing option.

setting => processing options.
This has five tabs 1. Spot finding, 2. indexing, 3. Processing 4. Advance Processing, 5. Advance integration.

initial three (1, 2, 3) tab has has ice ring exclusion options , you just need to check them that's it.

1. In the Spot finding => Automatic ice and Powder ring exclusion.
2. In Indexing => Exclude any spot rings.
3. Processing => Do not process spots near ice rings.

This will exclude your ice ring but you may loose some information from your data.

Good luck

--
Sita Ram

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From: Harry Powell

Hi

Actually, it's *much* easier than this in iMosflm (though Sita's suggestion is already pretty easy). There's no need to open the "Processing Options" menu in this case.

On each of the indexing,  the refinement and integration panes, there is a small button on the top row of widgets with what looks like a snow flake - click on this to activate ice ring exclusion for processing the data.

As Sita says, you will lose some information about genuine non-ice spots on (or very near to) the ice rings, but this is generally more than compensated for by the improved processing of the spots you actually do integrate.

Harry

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Dr Harry Powell, MRC Laboratory of Molecular Biology, MRC Centre, Hills Road, Cambridge, CB2 0QH

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From: Loes Kroon-Batenburg

Dear Shanti,

You may want to try EVAL (www.crystal.chem.uu.nl/distr/eval). It provides options to exclude regions affected with ice diffraction, or practically any region you'd like. In our experience data treated in this way have a lower Rmerge. However, the difference with respect to refinement statistics is not all that large, because ice-affected reflections are mostly rejected in the scaling step if you have sufficient redundancy. Ice scattering is rarely constant over theta-rings.

Regards,
Loes.

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