Re: [ccp4bb]: MIR phasing

["Eleanor J. Dodson" <ccp4@ysbl.york.ac.uk>]

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Ram Thaimattam wrote:
> 
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> Dear All,
> 
> I am currently struck at the patterson heavy atom difference map interpretation
> in MIR phasing. I have a native data set with data extending to 2.65 A, and
> two heavy atom derivatives, Uranium and Platinum have diffraction data extending
> to 3.0 and 2.9 A respectively. Scaling the three data sets (using scaleit)shows
> good statistics. The overal R-fact for U and Pl derivative data sets are 17 and
> 19% respectively. Furthermore there is a drop in the R-fact valuses at 4.8 A in
> both these data sets. However, when patterson heavy atom difference maps are
> calculated for these derivatives huge number of peaks are found in the map.
> There are about significant 300-400 peaks(>3sig) in both the heavy atom
> difference patterson maps. This is really anoying. I am not sure where exactly
> I am doing mistake. In this regard I request to kindly help me out to solve
> this  problem.
> Sincerely,
> Ram


 Have you used the EXCLUDE cards sensibly - look at the SCALEIT log
graphs to see if there are outliers, which MUST be excluded.

The GUI tries to do this automatically.
Also there is no needto calculate a Patterson using all the data - 10-4A
is usyally plenty..
Eleanor