Provided that you guess the number of copies and your guess is reasonably close, my experience is that Phaser will do the job. But you have to tell it how many copies you expect, or it will never make sense of the data. When I did my structure with 6(?) copies some years ago, I guessed a number that was close enough and then when I inspected the electron density I could see that there were more copies than I had told the software and all was fine after that. It was surprising to see that good solutions were obvious from a packing consideration, while inadequate solutions were obviously wrong.
Mark -----Original Message----- From: Ke, Jiyuan <jiyuan...@vai.org> To: CCP4BB <CCP4BB@JISCMAIL.AC.UK> Sent: Mon, Apr 30, 2012 2:28 pm Subject: [ccp4bb] Suggestions for solving a structure with 8-10 copies per asymmetric unit Dear All, I have a question regarding solving a crystal structure by molecular replacement. It is a single protein with a molecular weight of 25.5 kDa. The cell dimension is rather big from the diffraction data ( 90.9 Å, 143.9 Å, 216.3Å, 90°, 90°, 90°). The possible space group is P212121. With such a big unit cell, we predicted that there are 8-10 molecules per asymmetric unit. We have a decent model with sequence similarity of 49%. I tried several times with Phaser search with the current model and had difficulty to find any clear solution. Has anyone seen such cases and any suggestions to solve the structure? Thanks! Jiyuan Ke, Ph.D. Research Scientist Van Andel Research Institute 333 Bostwick Ave NE Grand Rapids, MI 49503
