On Tue, 20 Oct 2015 15:52:22 +0100, Mohamed Noor <[log in to unmask]> wrote:
>Dear all
>
>I have a low-resolution dataset to about 4.2 A processed with XDS. As all three of the CHI2-VALUE OF FIT OF CORRECTION FACTORS values were about 1.4, I processed the images assuming Friedel's law=false and STRICT_ABSORPTION_CORRECTION=TRUE. However, using Xtriage, the anomalous signal seems to only extend to about 12 A at the most. So, I have two questions:
>
>1. Can I process it by assuming Friedel's law=true?
technically, you can (i.e. nobody can prevent you from doing so), but it would seem unwise if you want to use the anomalous signal
Did you mean "should I use STRICT_ABSORPTION_CORRECTION=TRUE?" ? Probably you should not be using it, unless you have high multiplicity (let's say at least 3 or 4 observations of both I+ and I-).
>
>2. How can I know where the signal comes from? The protein contains Fe (about 11 atoms) and the dataset was not collected at the absorption edge? In fact, the structure could/should be solvable using molecular replacement and I don't intend to do experimental phasing.
Solve the substructure! If you can solve it, you know that it gave rise to a significant part of the anomalous signal.
best,
Kay
>
>I can post the processing stats if necessary. Thanks.
>
>Mohamed
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