[sharp-discuss] autoSHARP output - few questions

[Sundaramoorthy, Munirathinam]

This is a summary of my first ever autoSHARP attempt.  

I am working with a high redundancy and nearly 100% complete SAD data set of a heavy metal derivative (2.6 A resolution). The number of sites is not known but there are at least two sites as seen from the difference Patterson maps.  Both autoSHARP (RANTAN) and another program give at least 8 identical sites, including the two major ones I could interprete from the Patterson. But the differences in the peak heights between two major sites and others is huge. The first peak is 54 sigma, the second one is 10.5 sigma, and others are between 5-6. The initial CC (test) for 1 peak (> 40 s) is 0.214 and final CC for 5 peaks (> 6 s) is 0.243.  According to the manual,  this falls in “good” range. 

 

The FOM values  in the first and second SHARP runs are 0.357/0.218 and 0.322/0.197 respectively and the corresponding overall phasing power is 1.925 and 1.65. In the second run an additional site is found but not added as the number of sites exceeds what I asked for.

 

If I examine the log file, the phasing power after 3rd Big Cycle drops below 1 around 3.6 A.

 

The best and inverted hand score are 0.3894 and 0.3150. The final score is 1.8321 with the suggested solvent content.

 

Finally, automatic building gives “9 chains with 44 residues: 0 docked in sequence [R/Rfree 0.372/0.537] in 10 cycles”. 

Map doesn’t look interpretable at all.  

 

My questions: With the numbers above, does this dataset look promising for SAD phasing? Should I rerun SHARP searching for more sites and cut the resolution to 3.6 A, then do phase modification and extension to 2. 6 A resolution in DM? 

 

Further, I have a low redundancy and incomplete native data set at 2.8 A. Would it help or hurt to include this to try SIRAS?

 

Thanks in advance.


Sundar

 

 

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