This is a perfect case for potential static/statistical disorder. See
The 1.8 å crystal structure of a statically disordered 17 base-pair RNA duplex:
principles of RNA crystal packing and its effect on nucleic acid structure
1 Sapan A Shah1, 2, Axel T Brunger1, 2,
To investigate/solve this, you should run Phaser-SAD using partial model
phases, look for any anomalous atoms like Cl- or S, then auto rebuild to get
the right registration. This will only work, however, if the crystal is not
statically/statistically disordered. If it is, then you will see less-strong
peaks at several registers, and you will have a tricky case on your hands.
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Abhishek
Sent: Monday, September 19, 2016 11:48 AM
Subject: [ccp4bb] multiple similar solutions in phaser
I am trying to solve the structure of a collagen triple helix using phaser. The
crystal diffracts to 2.0 A in P1 space group. Matthew's coefficient suggests 4
molecules in the asu. When I tried to search for 5 components, phaser gave 8
solutions each containing 4 triple helices. The LLG scores are in the range of
2200 and TFZ around 15.
All 8 solutions are similar except that the triple helices slide either up or
down with respect to each other in different solutions.
Refinement of the top solution using default settings in phenix resulted in the
R-work: 0.5000 0.4003
R-free: 0.4989 0.4586
RMS(angles): 1.82 1.74
RMS(bonds): 0.013 0.009
I am relatively new to crystallography and would appreciate any help in
understanding why I am getting multiple solutions and if there is a way to
reconcile the results into a single solution.