Hi everyone! I have a question on my poor MIR map. Four datasets (two AU and two HG) were used for phasing upto 3 A resolution in my case. I could locate several heavy atom sites for each dataset with occupancy finally refined to about 0.3 to 0.4, and with B value refined to about 50 to 80. I did not include the anomalous data because once I refine against anomalous data, the anomalous occupancy was only about 0.02, and even smaller as 0.004 for some sites. I guess the anomalous data are not good enough, so I did not use them right now (Could I do this? Or must I include them somehow?).
The FOM I got is about 0.6, the Cullis-R factors were about 0.6 for all four data sets, and the phasing power was about 2.5 in each dataset. After I did the density modification, the FOM could increas to about 0.8. My problem is that the protein should form a long helix structure as indicated by other homology protein, but in the map after density modification, the densities are not consecutive though the overall shape seemed to be a long helix. The good thing is that some short helix-like densities could be observed in the current map, but they are not connected to each other. Right now, I am totally lost whether I should believe in the mir-map I have. Could I improve this map with some other method? Or should I re-do the phasing? BTW, the space group for my crystal is R3 or R32 with a=50, b=50, c=380, alpha=90, beta=90 and gamma=120. The c-axis is much longer than a- and b-axis, so the reflection data suffered from the anisotroy effect. Any suggestion on my phasing problem is welcome. -- Alphar Ni Call me alphar~ :)
