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, http://dx.doi.org/10.1006/jmbi.1998.2385
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. JPK -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Abhishek Jalan Sent: Monday, September 19, 2016 11:48 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] multiple similar solutions in phaser Dear all, 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 following statistics. start final --------------------------------------- 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. Thank you Abhishek
