Dear all, I am now trying to phase a structure in C2 using anomalous scattering at 5-6 A. It is hard to improve the derivative resolution at the moment. Shelxd is able to locate 6 sites with a distinct CC and FOM. After density modification in shelxe, the contrast of the two enantiomers is 0.59/0.38 for SAD and 0.7/0.3 for MAD. When I looked at the electron density, the maps from SAD and MAD are similar, and the solvent boundary is quite clear. However, the problem is that the electron density blob passes through the 2-fold rotation axis, even at 3 rmsd contour level. Also, the unit cell seems to be too small for the molecule. I am afraid that the space group assignment is wrong, but I am a beginner so I nearly have no clue. I did reprocess the data in P1 and looked at the self-rotation function with a radius at 200 A. From the list it seems that there is only one 2-fold rotation axis. I am quite confused. Could anybody give me some hint of this problem?
Thanks a lot in advance! Sincerely, Chen
