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I think any decision depends on the resolution of your two data sets. If
they are very different I would choose the higher resolution one.

If that is the Anom data then I would use the anom signal at least in the
first cycles to improve the phases..

Eleanor

On Thu, 3 Jan 2019 at 14:59, Piotr Wilk <[log in to unmask]> wrote:

> Dear CCP4 experts,
>
> I'd like to ask your opinion about using anomalous signal in refinement of
> crystal structures in addition to using high resolution native data.
> I am working on a series of structures for which I have collected two data
> sets (from the same crystal):
> 1 - native with higher resolution
> 2 - anomalous at MN absorption edge peak.
> The structures were solved with MR and preliminary refinement using the
> native data only yields decent statistics, but I also use anomalous data to
> verify presence and position of manganese ions. For this I used ANODE which
> lists four strong peaks (~30 sigma) as expected for manganese ions and
> around 45 weaker peaks (~9-5 sigma) for sulfur atoms in Cys and Met. I am
> happy to use this information in model building but I was also wondering if
> (and how) beneficial would it be to use both high resolution structure
> factors and somehow lower resolution yet highly specific anomalous signal
> in the same round of refinement?
> In Refmac5 I can use either refinement with "no prior phase information"
> taking FP and SIGFP or "SAD data directly" with SIGFP F(+) SIGF(+) F(-)
> SIGF(-), but I didn't find any "MAD" option to use both.
> I have the following columns in my mtz files:
> for native data:         H K L FP SIGFP FreeRflag
> for anomalous data : H K L FP SIGFP F(+) SIGF(+) F(-) SIGF(-) FreeRflag
> or :                           H K L FP SIGFP DANO SIGDANO ISYM FreeRflag
>
> I could use CAD to merge the interesting columns into a single mtz file
> containing:
>  H K L FP SIGFP FreeRflag F(+) SIGF(+) F(-) SIGF(-) DANO SIGDANO
>
> I'd appreciate any comments or advise how to use both sources of
> information in the refinement.
>
> I wish you all a Happy New Year.
> Kind regards,
>                     Piotrek
>
>
>
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