A question for data trimming

Interactive and automated data processing tools (PRIMUS, GNOM, AUTORG).
Scattering from simple bodies (BODIES), peak analysis (PEAK), data plotting (SASPLOT) etc.
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Donghyuk Shin
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Joined: 2013.04.12 13:58

A question for data trimming

#1 Post by Donghyuk Shin » 2013.05.01 02:53

Dear all,

I have a serious question that must be discussed, I think.
When we run AutoRG, It gave us a good range for nice Rg.
Then, does we have to trim the data file with the range we got from AutoRG?

e.g) I got data points from 1 to 897. AutoRG tells good Rg range is from 6 to 47.
Then do I have to make a data that has the points from 6 to 47 ??

I already tried to run DAMMIF with both original data, and trimmed data.
Of course, two envelope models from both runs are different.
And, It seems like that the envelope from trimmed data is more better than that of original one.

I also tried to know about it by myself. I am still finding and reading some saxs papers, and I read a good paper [Publication guidelines for structural modelling of small-angle scattering data from biomolecules in solution. Acta. Cryst. D. (2012)]. It looks like that we should present the good range for the Guinier plot (Of course it must be). For other plots ( ln I(s) vs. s , P(s) vs. s, Kratkhy plot etc.) we have to show the entire range of the data. Then, It seems like that I should use the entire data set for the envelope model.

Now, I need your help. Please give your kind help.

Best regards,
Donghyuk

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AL
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sas data range

#2 Post by AL » 2013.05.02 10:26

Donghyuk Shin wrote:e.g) I got data points from 1 to 897. AutoRG tells good Rg range is from 6 to 47.
Then do I have to make a data that has the points from 6 to 47 ??
More like points 6 to 897. Points 6 to 47 is the Guinier range that contains only the information about the radius of gyration of your particle. Lower angles contain information about larger distances in your particle, higher angles contain information about smaller distances.
You can crop the first 5 points e.g. using DATCROP. Make sure smin < π/Dmax.

The data range depends on the size of your particle and the type of modelling you want to do. As a rule of thumb for DAMMIF/DAMMIN modelling: smax = 7/Rg.
If you use DATGNOM you can specify how many points to skip (5 in your case) and the higher angles in the resulting .out file will be trimmed automatically.

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