Dear Rain, Maybe a little late, but here are some more comments:
1) What is the deal? For me, one can only know the space group after the structure has been solved. I have seen quite few cases (e.g. twinning, non-crystallographic symmetry etc.) that all programs (XDS, pointless) and statistics would insist on the wrong space group. Since there is a discussion on the space group, the structure has obviously not yet been solved, so why not say something like: most probably hexagonal or maybe trigonal? You could even give statistics for both possibilities. Based on diffraction data alone, it is impossible to determine the space group with certainty (at least for proteins). 2) Higher than expected Rmeas at high resolution also make me suspicious. In such cases I usually compare the statistics of the data processed in P1 vs. the data processed in a higher symmetry space group. If there is a big discrepancy at high resolution, there may be a mundane explanation like radiation damage or anisotropic diffraction, but it might also be that the symmetry which was thought to be crystallographic is in fact non-crystallographic. At low resolution, this symmetry closely matches crystallographic symmetry, but at high resolution, this symmetry deviates more and more resulting in much higher Rfactors. So in fact, you may have a lower symmetry space group with almost crystallographic non-crystallographic symmetry. In your case I would tell the referee that since the structure has not yet been solved it is impossible to determine the exact space group and leave it at that. Best regards, Herman -----Ursprüngliche Nachricht----- Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von <Rain Field> Gesendet: Mittwoch, 7. Mai 2014 21:41 An: CCP4BB@JISCMAIL.AC.UK Betreff: Re: [ccp4bb] Space group problem I thought there was a theoretical Rmeas number for I/sigma=2 that is around 50%? In my case, the Rmeas is much higher. Before, we reported P62(4) and got rejected. I'll just change a journal. Hopefully reviewer will not be too picky about that. Thanks to everyone!
