Hello Alexandra,
I believe you have to reprocess the data keeping friedel pairs (f+ and f- ) separate to make use of the little most anomalous signal (if any) at your collected wavelength. The best thing would be to collect a high redundant set of peak data (if not all the three data sets including mad remote and inflection data) If you have access to a tunable source and xtals left. Once you process differently, you can do all sorts of substructure search and later refine anomalous scatterers using wavelength, atom type and f ' and f“ values. Sulphur sad is also a good possibility if you have a decent nmbr of sulphurs in your protein.

Hope this suffices your query.

Regards
Ashok Nayak
CSIR CDRI,
Lucknow, India

Alexandra Marques <at.marques@fct.unl.pt> wrote:

Hi,


I am in the last refinement steps of a MR model and I want to calculate an anomalous difference map essentially to confirm the presence of a sulfite molecule and to locate vanadium (present in soaking solution). I read that it is necessary to have a mtz file with anomalous data (i.e. F+,F- or I+,I-). However, my data was collected at “normal” wavelenght (0.97) and it was processed with XDS considering Friedls law= true and my mtz file contain the following columns: H K L FP SIGFP. So, can I still calculate a anomalous difference map based on my data?


Since I also have a Mo atom in the active site can I try to refine its occupancy by using the option “anomalous groups” in the refinement strategy?


Thank you very much,

Alexandra