Dear Randy,

Thank you very much for answering. I followed your suggestions but, unfortunately, I couldn't get a reasonable electron density map after MR and refinement.

First I would look at the data to see if you have ice rings, because the peak in mean intensity and second moment of the intensity at about 2.25A resolution suggests an ice ring problem. If so, you should make sure you don't contaminate the data with spurious large intensities.

Indeed, the data has ice rings. At first, I required imosflm to remove ice rings, but it didn't happened. So, I re-processed the data in different space groups removing the ice rings.

Second, the statistics (e.g. the second moments plot after tNCS correction in Phaser) would be consistent with a scenario in which you have pseudosymmetry along with a twin operator that parallels the pseudosymmetry. If that's true, it's hard to be sure of the symmetry. For instance, if the structure really is monoclinic, can you be sure you chose the correct axis to be the 2-fold?

I am not sure. However, I tried two possible axis to be the 2-fold and none of them gave me reasonable maps after MR and refinement.

Since you have a good model that gives clear MR solutions even in P21, you can probably process the data in P1 and solve it with 8 copies in the unit cell. Then you can look at the symmetry of the MR solution (e.g. in Zanuda) and see whether it obeys any higher symmetry than P1.

I processed data in P1. After MR (with 8 copies in the ASU), it resulted in TFZ=11.6 and LLG=1434. But the map is still bad and high Rwork and Rfree.

According to Zanuda, the data should be P21:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   | >>   4   | P 1 21 1   | 68.6868  |  0.6289  |  0.5487  |  0.5523  |

   ---------------------------------------------------------------------

   |      1   | P 1        | 69.4151  |  0.6171  |  0.5471  |  0.5559  |

   |      4   | P 1 21 1   | 69.3810  |    --    |  0.5482  |  0.5442  |

   |     11   | P 21 21 21 | 52.0271  |    --    |  0.6107  |  0.6178  |

   ---------------------------------------------------------------------

   | <<   4   | P 1 21 1   | 69.3810  |    --    |  0.5482  |  0.5442  |

   ---------------------------------------------------------------------

I processed in P21 using two different unit cells, and MR resulted in TFZ=20.8 and LLG=511, and TFZ=56 and LLG=2867. However, again, no good maps and statistics.

Best regards

Marcelo Liberato