I think I have a pseudo-centering problem.
I have a 1.6 ang. dataset of a mutant protein that is an homodimer in solution.
Data processing gives the following SG:
Space group: P 31 2 1
Average unit cell: 111.36 111.36 28.56 90.00 90.00 120.00
Average mosaicity: 0.24
Rmerge Overall 0.07
However with this SG the unit Cell is too small and monomer doesn't fit the in
I reprocessed the data in other possible SG (including P6) and finally I got 2
equivalent SG's in which I can get a correct Molecular Replacement solution:
Space group: I 1 2 1
Average unit cell: 57.07 111.11 192.90 90.00 90.07 90.00
Space group: C 1 2 1
Average unit cell: 201.10 111.11 57.07 90.00 106.42 90.00
Both with Average mosaicity: 0.38 and Rmerge Overall 0.06,
but the corresponding MR solutions do not refine, with R-factor stuck to 45-47%.
From what I understand, in the I121 SG I have the NC two-fold axis of the dimer
at 1/2a and this originates the pseudo centering and the small P3 Cell
Largest Patterson peak with length larger than 15 Angstrom:
Frac. coord. : 0.500 0.000 0.000
Distance to origin : 28.566
Height relative to origin : 53.830 %
I'm really not so good with symmetry, so I'll be grateful for any
suggestion/help/solution from you out there.